How can I invite friends to the game?

You can invite your friends to the game ( those, who don't play the game yet). To do this, just click on the "Friends" tab --> Invite friends

"Select All" is chosen by default. You can remove the check mark and choose the certain friends from the list. Then click on the "Invite" button to confirm this action.

You can get 30 Credits for newly joined player, Credits are awarded when the friend reaches level 3.