How do I use OBS to push streams?

You should make sure that your camera is working in OBS.
Click on the Facebook page in sequence as the picture shows.

Open the platform you want to stream and get the platform’s URL for Sever and Stream key for Stream Key.

Save all the settings and click Start Streaming.

For example, you can get YouTube’s Stream URL and Stream Key as seen below.

https://www.youtube.com/watch?v=Y8_KEIMrnsIhttps://www.youtube.com/watch?v=2kdty0wL7m4&t=26s