There appears to be no way to join a pvp match with your friends. Best you can do is join a friend who is already in a lobby, but that is hard to do as the games fill up quick. We spent an hour last night trying to get 3 people into the same game. This seems like a glaring omission.
The pvp is really enjoyable but to keep people around, you need to be able to join a game/lobby as a group.
Here is a reddit post about the issue:
http://www.reddit.com/r/farcry/comme...with_a_friend/