Q: How do I add my Ipod touch to my device list

Your device list where?

Where do you want it to appear?

is this a new iPod? Or one previously owned/

previously owned iPod doesn't appear as a device on iMac.  Trying to download an app for the first time on iPod and can't get it to work.  Thought this might be why

What iOS version on the iPod?

What OSX version on the Mac?

Where are you expecting it to appear? If iTunes then:

If iTunes doesn't recognize your iPhone, iPad, or iPod - Apple Support

Was this done to the device?

What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support