There are a few different ways to do this, but first you really need to add a bit more detail before one can really answer. Do you want the link to the coupon page to be a part of your menu system, or are you trying to add the link into an article on the page or an element? Is the page going to be a coupon page that you've created on your own website, or are you trying to link to an "external" website owned by someone else? The more detail you give when asking a question, the easier it is for people to help.
