how do i transfre music to my new ipod from my old one

I have had an ipod nano for a few years now and decided to buy a touch and I want to know how to transfer my music on to my new one. when I connect the new one to the computer my iTunes thing on the computer doesn't seem to know its there ( can you tell im not very tech savvy) so how do I sync the new one to the exsisting stuff, hope that makes sense.