There are 2 ways to access the coupon area where you can create coupons:
Go to: Site or Courses > Coupons > Create Coupon
Both ways lead to the same coupon area on the site.
For example, while in the site interface, selecting courses from the left-hand side changes the menu, but selecting coupons takes you back to the site interface.
Also watch the video on 'Creating Coupons in Zenler'