A promo code is what you get from us or our partner vendors to apply discount to our products and services. When placing an order, just before you checkout, there is a field for you to apply a promotional code when you have one. A valid code will save you money one time or reccurently depending on what the promo code is for.
Once you have a promo code, place an order for a new web hosting plan from GigaLayer and proceed with your order like you normally would. Only remember to apply the discount before checkout! It's just that simple.