Fingerprint readers, I think, are actually small scanners. You would capture their output using TWAIN (Technology Without An Interesting Name) standard. I don't know the specifics of it, but try searching the web.
Once you get the output (a bitmap) dealing with it as a fingerprint is not an easy task. First of all, you would need to do lots of research in fingerprinting science. You can not just compare entire bitmaps. That would never work. You need to determine some key point of each fingerprint, store that in a database and compare those key points.
Then, you would need to transfer that into some fine image analyzing code, not an easy task.
Anyway, I don't think there's way that a good program of this kind can be simple.

If you still want to do it (not that I meen to discurage you),
Good luck!