You need to enter the voucher code exactly. There are 2 positions to enter the voucher code:
At your cart
At payment step
Step 1: Go to Checkout by hovering over "My Bag" icon and clicking on "CHECKOUT NOW".
Step 2: Fill in all the necessary information until you reach the section "REVIEW & PLACE ORDER". Then, go to "APPLY PROMO CODE?".
In addition, you can directly add credit point the Wallet by: