I can't get my ipod nano to sync with itunes 11

I have an ipod nano and I just got a new computer so I had to download itunes again (itunes11). I just purchased some new music and I can't get it to sync with my ipod. I have activated the new computer and when the ipod is plugged in, it registers that it's mine, but whenever I go to "file" and then "devices" the "sync" option is greyed out and it only allows me to "transfer puchases from my nano". How do I get this to sync?