Do you want to learn to stream? I've made a step by step guide that covers how to set up and use OBS to stream to Twitch. It covers how to route audio from whatever application to OBS. There are sections on Windows, Mac and Linux.
This is aimed at beginners to streaming (specifically students in my classes) and I would *love* it if you tried it out and sent me your questions. Or did I get something wrong? Let me know! Your questions and complaints will make this more useful to everyone.