Hello, I couldn't fully understand your question but if you're looking on how to start a game, in a lobby, you usually click on another user, and then click Challenge.
Then the other person has to accept your challenge and then you'll start playing!

If anything you can also be challenged and you'll receive a pop up which would give you the options to Accept or Decline, and it will show the user who is challenging you. If you wish to play with that player, you would then hit accept and the game would start, if you do not wish to play with that player, you would then hit decline, and search for another player to play.

As i stated in the beginning, i couldnt understand what you really wanted, unless it was an issue like your connection or something, then i can't really help you in that.