if you are using an unhopped kit, and have access to a good sized stock pot, you can reconstitute some or all of the can in water, boil it on the stove and add bittering / flavouring / aroma hops as desired.
If you are using a hopped kit, then I would not bother. but if you must add more bittering to a hopped kit, then I would go down the path of making up a water and dry malt extract mix, boiling that in a stock pot, and adding your hops, then add that back to your kit in the fermenter.