Way to join friends

Hi, so I just started playing this game today, and I couldn’t figure out any way to join my friend? He joined a while after me and I wanted to help him out, but couldn’t seem to get in his game. Since we can’t friend join from the site, I figured there’s gotta be a way ingame to do so, but couldn’t find one. If there is one could someone please tell me how? And if not a way to join friends should definitely be added. Thanks for reading and possibly responding.

I’m pretty sure the game prioritizes joining servers with your friends. If you couldn’t join his server it probably means it was full.