So this is on for PS4 tomorrow night then? Who does the invites?
Bit weird playing on PS4, I'd got used to playing with PS4 controller on PC, but using gyro for aiming. Just using the right stick sucks donkey balls.
Once you're more integrated in to the group and have more names on your friends list you'll see who's online and just hop in, or they'll invite you. Usually whoever's online first makes a party and everyone else just piles in until it's full at which point we send invites to the actual game lobby and use in-game chat (20 people all talking rubbish can be a hoot).
I'll add you tonight and invite you tomorrow, your friends list will grow like mad after that and you simply hop in to whichever party is playing the game you want and get stuck in.