it's not that hard to do actually. however remember you're dealing with electricity, as such you may want to have someone check your handiwork after you're done. as john suggested you'll likely need a 3 pronged plug. hopefully there are 3 wires coming out of the fixture, one hot, one neutral, one ground. if there is not a ground wire then i would go back to the store where you bought it and ask for a length of wire suitable for a ground, and also it may be good to ask the salesperson where the ground wire should be attached to the fixture.
there is a variety of plugs available for such purposes. generally to attach one you will need a screw driver and some sort of wire stripper. there should be directions included with the plug.
this sort of repair is quite often covered in electrical diy books. if you need any further info let me know. however i'd like to suggest that if this info is over your head, don't do it yourself, take it to someone who knows what they are doing. i have gotten a couple of very painful shocks whilst wiring my ballasts.
also i suggest a gfci unit for your electrical outlet. do a search for gfci if you're not sure what this is. good safety feature.
ps i just reread john's post and he actually suggests a 3 prong extension cord. well that would work too, but the last time i looked i couldn't track one down in a number of hardware stores. if you want to use the 3 prong extension cord, you should splice the wires together inside the fixture with wire nuts.
hope that helps.