Custom Log-in Method


I am looking at designing a log-in implementation based on our retired chat service’s login. I am new to the way Rocket Chat works on logging a user in. The old web chat had a method which, based on four items of code, would authenticate the user, set their name, set their avatar, and set a profile URL. Is there a way to do this (as the users would be signing up through the main website, not the chat directly).

Thanks in advance!