Well, there are plenty of tutorials to do it directly, so I am going to focus on a case, where there are “special circumstances” – like, you want to mix external microphone and your phone, on your computer and send it to Youtube. And of course, this will be quick & dirty.

Prerequisites:

(1) YetiX (https://www.bluemic.com/en-us/products/yeti-x/)

(2) Epoccam (Pro) (https://www.elgato.com/en/epoccam)

(3) OBS (https://obsproject.com)

First, you connect your computer with your phone via Epoccam. With pro version, you can choose how to connect (USB/WiFi), otherwise it autoselects WiFi – may not be useful in scenarios, where you have weak internet around.

Then, you add new devices in OBS (your Yeti and your Epoccam) – name them and turn off every other device which can give you input.

Then, go to studio.youtube.com and create a live event, selecting that you will stream via streaming software – somewhere on the right, you will be able to share the link towards this live stream.

Finally, go to OBS, selecting all the inputs you want, and select start streaming – the menus will take you to manage streaming first, where you will select the one, that you just created.

Warning: you may have to wait for 24 hours in order for streaming facilities of Youtube become available.