adding friends??

[TCEd]

Hello to COD community, very noob question, got the game from a friend as a gift, he's also a noob with this game, we can't seem to figure out how to add each other to our friends list, tried right clicking on his name, reading the manual that came with the game, ect... but nothing on adding friends, can't figure this out, how do you add friends ingame?

Thanks for the help, got loads to learn about this game & this is the first step.