Well, if you find players in the game, when you click on them there is an add friend option. This can be risky, they may think you are inviting friendlies, and might even play them against you at inconvenient times. So there's that, but I have added friends this way.

You can also use the add me thread on the forum, when people post their link, often specifying if they want friendlies or not:

http://forum.topeleven.com/add-some-...er-2013-a.html