Go to "Transfers" in your mobile application, click on "To a new contact". Enter the data of the new recipient. Confirm the operation by putting the passcode that you use to login to the application. The new recipient is now added. If you do not want to send any transfer to this person right now, just go back from this screen. 

Do I always need to add the recipient to my list when I make a transfer?

Yes, to make the process as easy as possible, you need to add recipients to your database when you pay them. You can delete a recipient at any time.