how do i add tunes to my computer library from my nano

Are you asking how you add the content from your Nano to the iTunes library on the computer? You would download the iTunes program on the computer from the Apple website. As far as content is concerned, that is done via iTunes, purchases, or you rip content to the library from you CD collection. iTunes is designed for a one-way sync, from iTunes to the device, not the other way around. If music is purchased from iTunes, then log into iTunes on the computer with the device connected and transfer your purchases.