Help with syncing iPod Touch 5g

I just got a iPod Touch 5th generation. I still use my 4th generation as well. Is there a way that I can add my new iPod to my account and sync my music?

When I first plugged the iPod in I did get the option to set up as a new iPod or back up from the other iPod. I chose set up as new since I still want to use the older one for work. I leave one at work and keep one at home/with me when out and about. Now I cannot get my PC to even acknowledge the new iPod. How can I correct this?