an easy way to go, as in what I would do, would be to use a wall wart and a PC fan. If you do go this route, make sure its between a 5VDC and 12VDC wall wart, you can then just clip the plug off the cable and splice it directly to a leg on the fan. As a note, + is usually red and - is usually black, If you have a multimeter, you can check the polarity of the adapter with that. I would also recommend this is you are much less likely to hurt yourself or burn down your house.
If you do go with a 120VAC fan, Keep in mind that Black is hot, White is neutral, and green is ground, Though, if your not sure about that, find a friend who knows better and ask them to help you out, Its a good way to learn and your probably much better off