To redeem a deal, search for the course and click on the course picture which will take you to the Deal Details screen.  When you get to the golf course and check in at the pro shop, show the golf course attendant your phone and they will click on the "Redeem at course" button. 

You will be prompted "Are you sure you want to redeem this deal?"  The golf course attendant will click "Redeem at course" for a second time.  This will Redeem your deal. 

After you redeem a deal, one of the plays will be marked off and indicated with a filled in circle and a checkmark.