HT1329: How to use your iPod to move your music to a new computerLearn about How to use your iPod to move your music to a new computer
Currently Being ModeratedJan 20, 2013 7:06 AM (in response to Mich22)
If you're using iTunes 11 click on the box icon in the top-left corner to see the " Show Menu Bar "
and from the Menu Bar select Store...
From the Store menu, choose Authorize This Computer.
When prompted, enter your Apple ID and password, then click Authorize.
See Here for full details...