How to make a "join friends party" sistem

i am making a game and i expect that a lot of people will play it, i used the normal way, i made a GMS object, and a login/lobby room, but i realized that everytime anybody logins in the game he automatically joins in to my party, and that makes the game start inmediatly with the first person who logged in, i dont wanna that, i wanna that you can join and then select if you wanna play with a random person, or play with a friend, and i dont know how because in the exactly momment anybody connect, he inmediatelly joint into my team.

How can i do that?