Your vouchers are all saved under My account > My vouchers
All that is left to do it to copy/paste your discount code in the dedicated bar on your shopping cart before finalising your order.
I invite you to double check your order summary on the right side of your screen when you place your order to make sure your discount is well taken into account.
If you face any issue, come back to us before placing your order and we will be happy to assist you !