I would do a forum search as this has come up before - simply look for "barcode". First, you'll need a barcode scanner (a hardware device). Most come with software that make them act like a keyboard. The user presses a button to read a barcode and the text is spit out to the computer as if the keyboard typed it. There isn't any special software, usually, beyond that basic functionality - at least not in my experience.
-ner