So Usually You'd Go To The Multiplayer Online Menu, Right Click People There, And Add Them As A Friend.
This Doesn't Work At Present, Because No One's Playing It Anymore.
So Click Multiplayer, Click Online > Then Bottom-Left, There's An Add Friend Button.
- Type Anything You Want To In This Field And Hit Enter.
After You Type In Any Nonsense "Username", The Achievement Is Yours!
Good Luck!