OBS Camera is an add-on for OBS that allows you to use your iOS phone as a video recording device. You must use OBS Camera with the desktop version of OBS which has Mac, Windows, and Linux support. There is a one time purchase cost for the app at $15.99. We think it's worth it to get a high quality app like OBS Camera vs using a free app like Streamlabs OBS.
Once OBS Camera is installed as an add-on, you can use USB to make your iPhone a source to use in OBS.
While it can be done wireless, you'll need really good upload speed on your wireless network to get 1080p streaming. This should be easiest using a computer that is hard wired via Ethernet cable.
You will probably want to check out a website like www.monoprice.com to get 10 foot+ cables for this.
Finally, we're going to provide instructions for setup via the obs.camera site. There's multiple options on how to do this so we think it's best if you read it right from the builders of the app:
Now once you've got the add-on working, you can proceed like normal with streaming from OBS to Uscreen. Instructions here for setting that up.