Originally Posted by Ooompa Loompa
Well, if it needs them added (and you won't know 100% for sure until it's done fermenting, but I think it will need them) then you'll probably want to buy an ounce or two of hops (I'm thinking centennial hops would work well, and should be obtainable) then put them in a quart or so of water, and boil for an hour (basically making a hop tea) then add the "hop tea" to your beer.
Unfortunately that will NOT work. There has to be sugars in the solution to isomerize the hops.
Either just add some hops as a dry hop for a bit more flavor/aroma or mix dme into some water and boil with some hops for an hour if you need more bitterness.
Odds are this will be quite drinkable without making it more bitter. I would dry hop some hops though for aroma and a bit of flavor as the original kit is lacking in that department anyway.