While you are connected to Facebook, GameCenter or Google Play you are able to see in-game your friends playing NHL Figures. 

To play with your friends, go into the friendly match menu. In your friends list, your friends with a green badge means they are playing the game.These are more likely able to answer to your invitation. 
While sending an invitation, you can't send another one. If your friend doesn't answer, just cancel it and to be able to send another one.

At the end of each friendly game, you could replay with the same opponent to get revenge.