Hey hey, you have to click multiplayer and after that, quick match. If you get stuck on Connecting, you will have to restart the game, it is a bug I will fix in the future.
If you don't connect to your friends room, get back to the Multiplayer window, and press quickmatch again.
If you and your friend press quickmatch at the same time, both creates a separated room.
To the end of the game jam delivery time I just had time to create quickmatch system. Your friends just have to do the same. 4-5 people can join the game ( I actually don't remember, I set up that on the players limit a month ago, at the beginning of the project)