This achievement is so easy, doesn't need any interaction between players (cause your friends request don't have to be accepted) and it will take you about 3 seconds.
You only have to log in with your account and click on any active game to see the in game players, then press right-click on any player portrait, finally click the add friend option... and you'll have your first Tochlight II friend,
Repeat this an other nine times and you'll get the achievement:
Just repeat this an other forty times and you'll finally get the achievement: