There are two ways. One way is you can go to the persons profile page and above their picture all the way to the right you will see a tab that says "add as friend". Click it and it sends a friend request to that person. And if he or she accepts it then that person will show up on your friend list. The other way is during game play. If you click on their name in the upper left hand corner of the screen where it keeps your score a mini profile pops up. And at the bottom of that profile is another tab that says "add as friend". Click it and a friend request is sent to that player and he or she can accept it while you play. If they do, again they will be added to your friend list. Hope this answers your question. Good luck and have fun.