Do you mean the 10% off?
It will automatically show in the final pay screen, if you are ordering on the App (up to a max $20 discount per order).
Otherwise, $10 coupons can sometimes be won during TT’s Happy Hour, which is held a few times a year, and on rare instances of a HUGE customer service screw up, sometimes, they will send a $6 or $10 coupon as an apology.