Move your library to another computer
There are a few ways to transfer your iTunes library from one computer to another:
When you get a new Mac, use Setup Assistant to move files—including your iTunes files—from your old computer to the new one.
Connect computers (over a wireless network or with a cable) and copy your iTunes files from one computer to the other.
Use a portable drive or iPod to transfer iTunes files.
Copy iTunes Store purchases from your iPod, iPhone, or iPad to a computer
Connect the device to the destination computer.
Make sure the destination computer (the one you want to transfer items to) is authorized to play iTunes Store purchases (choose Store > Authorize Computer and then click Authorize).
Do one of the following:
If the iPod, iPhone, or iPad is synced with another computer, or is an iPod shuffle: Click Transfer Purchases in the window that appears.
If the iPod, iPhone, or iPad is set up to manually manage items: Choose the device from the Devices pop-up menu near the top of the iTunes window, and choose File > Transfer Purchases From iPod (or iPhone or iPad).
You can play iTunes Plus songs on any number of computers; you can play other iTunes Store purchases on up to five authorized computers.
Before you sell or give away a computer, don’t forget to deauthorize it (choose Store > Deauthorize Computer).