How to authorize iTunes in Mavericks (OS X 10.9)? I've got my new iMac OS X 10.9
I'm using iTunes on my new iMac, running Mavericks. I would like to download music/movies which I've purchased.

But then a pop-up displays:


  Your computer is not authorized; You must authorize this computer
  before you can download previous purchases.


How can I authorize my computer?
'
Open iTunes
Find the Store menu
Select "Authorize This Computer" and enter your Apple ID and password.