When Viator is do the mapping on their end, they will ask you for Product Code and Option Code, for you mapped products.
Product code is the ID number of your product in Bókun. You find this number in front of the name of your products on your Tours & Activities list "Products -> Tours & Activties"
The Option Code is the ID number of your departure times in Bókun. This number is in-front of the departure time in your product: