You can only create games here in this forum section. Each tread can have one game going. So if you create a thread you could call it something like Play Connect 4 and then when you are in the thread just click Create Game.
Just click create game and then you can wait and see if someone joins. Or you can click invite and ask the user directly. When your done with game click the X on the right to close the game.
Pictures below show where all the buttons to create a game and invite a user are.
I included where you can see if someone has started a game and is waiting on anyone to join. You can see that on the forum main page.
If one game is going you can start another one at the same time. Just create a new thread in the game section and then you can create a new game .