I can't find out how to log in to Restream via my Facebook account. How can I do this?

It's not possible to log in to DJM-REC with Restream accounts created through Facebook integration.
You can log in to Restream with DJM-REC if you've linked your Google account or created an account with your email address.
Create a new account on the Restream website through Google account integration or with an e-mail address.