Board Thread:Help!/@comment-26037521-20150124015314/@comment-3509554-20150131031902

Yes, if your friend server is a Locked Server, you should create a character to be bound to it, and then play.

If not, try to see the affix on the world name, if have #, then the world is Free Mode, if have &, then it's Classic world.

Either way, you would need a character of that game mode, or bind a newly created character to that server and then you will be able to join.