Adding hops to your coopers beer kit is a great way to enhance the flavor and aroma.  This is especially true for hoppy beer style like pale ales and IPA's.  Dry hopping a beer is as simple as choosing a variety that has a flavor you like and adding it into your fermenter 3-5 days before you plan on bottling or kegging your beer.  A lot of people choose to put the hops into a sanitized muslin bag in order to keep the hop particles from going into your beer bottles.