If you look inside the fixture there should be and indecation of live and neutral .
In Britan live is Brown With Neutral bing Blue and a green n yellow earth , i don,t know what the colour codes for wiring are in the states but if you don,t know then don,t bother going any ferther get sombody who does.

I'll asume you do so Black is the live and white is the neutral with the earth screwed to the metal body anywhere as long as you have a good contact.

Oh and you can grow some nice bud with floes as long as you got enough wattage regardless off what anyone says to you. You need to be looking at 250-300w.
The ideal thing is an old sunbed that sombody is glad to get rid of , and all you have to do is replace all the tubes and your away for about £15.

Just use cool whites for the growing period and when they are a third of the size that you have room for start the flowering cycle mixing the cool whites 50/50 with warm whites