My Notes on Configuring OBS (Open Broadcaster Software) For Live Facebook Streaming (notes, not exactly a tutorial, but yeah it's kind of a tutorial):

Like other musicians looking to do mini-concerts on Facebook, I wandered down the path of looking at OBS. There are dozens of videos and articles about it, and I found that none of them really told me what I needed to know in the way that I needed to absorb it. We all process information in different ways. This is the info that would've saved me hours:

• I wound up looking at OBS because doing Facebook Live from my iPhone was trivially easy and worked pretty well and sounded pretty good, but I wanted it to sound better, and that meant using an external microphone.
• I bought an open-box Fifine 669B USB condenser mic (another story), but to use it, I needed to plug it into not the phone but my computer, and THAT lead me to using Facebook Live not on my phone but on my PC.
• For a number of reasons, I found that, whether I used the new USB mic or the one on the laptop, the sound in FB Live was horrible. Many folks report that FB's compression algorithm does strange things, but in my case, the audio was so inconsistent that it was completelyunusable. I switched mics, I switched laptops, I hard-wired the laptop to the router instead of using wireless, it didn't matter. In addition, my FB live video stream from my laptop's webcam was horribly jittery. Friends of mine said that they did not have this experience with either the audio or the video, that FB Live worked okay on their laptop, and that they gravitated to OBS to get a more consistent audio and video stream, but that it was a more subtle issue of data quality than a binary works / doesn't work issue. Whatever the reason, FB Live on my laptop without an external stream source was out of the question for me, and THAT lead me to OBS.
• You need to understand that OBS is a very flexible piece of software that allows you to do things like capture multiple video and audio sources and send them to different places. You can use multiple cameras, capture your computer screen, do split screens with you narrating a PowerPoint presentation if you like. So simply grabbing the laptop's webcam and microphone input (or an external mic) and streaming them to FB Live is just scratching the surface of what it can do. But what it means is that there's configuration and a learning curve involved. It's much more involved than just grabbing your phone, hitting the "Live" option in Facebook, and going. So you need to allocate some time to it.
• Jim Henry's OBS tutorial on Youtube is a pretty good starting point (https://www.youtube.com/watch?v=pz0p0Usr8X4), but a quick blow-by-blow is:
• Download OBS for your OS and install it, selecting "autoconfigure."
• Under "Sources" at the bottom of the screen, click on the "+" and select "Audio Input Capture" and select a microphone. Note that, with the PC's mic, an external USB mic, and the one in the webcam, you may have several.
• Then select "Video Capture Device" and select a camera.
• In the "Audio Mixer" panel at the bottom of the screen, the blue sliders are the input levels of the microphone(s). If you're plugging in an external mic, it's important to slide the levels of any other mics (like the one in the computer) down to zero, or strange things may happen. You can then hide them by clicking on the little wheel and selecting "hide." You can also disable them in Settings | Audio | Devices.
• If you've set up a camera and a mic, should see the image from the camera in the OBS screen in the black "canvas." I found that the webcam in my laptop was horrible. I remembered that I had an old Logitec 720p external webcam, and connected it. I selected it and it looked much better, but this kicked off a two-hour-long process to figure out how to get it and the "canvas" the same size so the stream into FB Live didn't have black bars on the side. All the jiggering I did of camera resolution and output stream resolution didn't fix it. Right-clicking on the image and selecting, I think, "Preview Scaling | Scale To Window" finally did.
• This is crucial: You can then play around for hours with camera and mic placement WITHOUT DOING ANY LIVE STREAMING INTO FB by hitting the "Start Recording" button on the right, and just watching and listening to the recorded video in Windows (it dumps the output into the "video" folder, at least it did with me, from where you can quickly click on them and view and listen to them). This saved a lot of time, as it took FB live-and-playback out of the iterative loop. I found that my $27 open-box Fifine condenser mic really wanted to be fairly close to my face but needed to be a little above my head in order to hear the vocal over the guitar.
• If there is a delay between video and vocal. you can sync them up by, in the audio mixer panel, right-clicking on the cog for "Audio Input Capture," selecting "Advanced Audio Properties," and adding a sync offset. Many people report that a 200ms delay in the audio is needed to make it sync up with the video.
• Once you have the sound and video configured so that you like the way it sounds in the recording, THEN you can stream it into FB Live.
• How laptop FB (as opposed to the phone app) does live streaming has changed recently. Under "Create Post," click "Live Video." This takes you to "Live Producer" who, like any live producer, first forces you to do a porno. Just kidding.
• Click "Use Stream Key." Under "Setup Options," click "Use a persistent stream key" so you don't have to keep re-entering it in OBS. On the right, under "Stream Key," click "Copy." Facebook should say "Waiting for live video."
• Then go to OBS, click "Settings," click "Stream," under "Service" select "Facebook live," and copy in the stream key.
• In the OBS main window, click "Start Streaming." In about 10 seconds, you should see the stream appear in Facebook.
• In FB, on the left side of the screen, to test this out, under "Privacy," select "only me." Then click "Go Live." You should then see the live feed. When you close it, you have the option to save it. You can then listen to it and tweak things accordingly, but as I said, the tweaking cycle is much faster if you simply record in OBS and listen without going through FB.
• As I posted in my question last night and many answered, the delay in the FB live stream as compared to what's coming into OBS is much longer than one would like. I'm seeing about ten seconds. I'm told, basically, get over it. Look at the OBS window not the FB Live window, and let go of the idea that you can interact with comments from viewers in real time.

This should get you up and running. You then can google "OBS settings for Facebook live," play around with the six or so other video and audio parameters folks tell you you need to change, and see if they matter. For me, the issues of mic placement and getting the OBS canvas to match the webcam size were far more important.

Good luck!