If you have received a discount code / gift card, this must be entered before you complete the booking.
Details and price estimates for the task will be on a blue stripe through all the ordering steps (almost at the top of the screen). Tap anywhere on this blue stripe to get all the details about your job. At the bottom you will find a button that says "Do you have a discount code / gift card?" . Tap on it and enter the discount code or gift card code.
Details and price estimate for the task will always be on the right side of the order if you order via computer. Click on "Discount code / gift card?" just below the price estimate to enter your code.