Enable Coupons in Membership Offers
On your Dashboard, click on Memberships > Courses > then Offers
Click on the Offer that you wanted the coupon to be enabled
On the right side of the screen, look for the "Allow checkouts to access coupons" option and toggle it on then click Save
Enable Coupons in Funnels or Website
On your Dashboard, click on Sites > Funnels or Website
Click on the funnel page or web page that contains the 1 Step or 2 Step Order Form
Click the 1 Step or 2 Step Order Form and switch to the Advanced tab on the right panel
In the Advanced tab, scroll down and look for the Coupon Options Section
Toggle on the "Enable Coupon Codes" option
Click Save and Publish