Click "ADD COUPON"
Fill out the form
Code: string without spaces Fee percentage: How much will the discount be? Expire Date: When will this coupon be available and expire? (try to avoid creating very long coupons)
Now, send the link to the customer, ensuring that you replace [COUPON_CODE] with the name of the coupon you just created: http://gitcoin.co/new?coupon=COUPON_CODE