You can add/invite your friends through facebook or by using another player's friend code. To access the friends menu and your own friend code, press the top left button with two white persons as an icon. This will bring you the menu where you can see your friends and those that are pending at the moment.
Your own friend code is listed at the bottom of the menu.
My Friend Code: xxxxxx //Where xxxxxx is your friend code
You are welcome to add me if you don't have anyone to start out with: dewvoo2 or those that are posted in the comment section of this page.
Friends of friends
Only have one friend online, but you want a full party? Your friend can also invite someone to your party even if you don't have them on your friends list! You will be given the chance to add/accept them to your friends list from the party list once they join it.
Benefits of having many friends:
Taps sent from friend's devices will act as an extra tap against the monster you are currently fighting. This means they will deal the same tap damage as your player hero. When farming monsters, your friends will do 100% of your tap damage. When fighting bosses or participating in a dungeon, your friend's taps will only do 10% of your tap damage.
Sharing "Make it Rain" and "Power of Holding"
When using the 'Make it Rain' skill while in a party, you will share the wealth with your friends in the party. Each friend in your party will receive 10% of their own 'Make it Rain' amount. Additionally, if you use the Power of Holding, your held taps will also be sent to your friends.
Active skills do not affect your party members (outside of tap damage bonuses).