How to Set Up a Separate iTunes Account

Method 1 of 2:

Launch your iTunes software. Double-click the iTunes shortcut to launch it.
Create a new iCloud account. You'll need to create this account on the device you wish to use iTunes on. Navigate to "Settings" on your device, then iCloud. Enter the e-mail address you'd like to use as an alternate Apple ID.
Sign in with your Apple ID. Make sure this is the ID you want to use for purchases. Head to "Settings" then tap on iTunes and App Store. Sign in with the Apple ID you want to use.

Method 2 of 2:

Log into iTunes on your computer. In iTunes, click on "Store" in the Menu bar at the top and click "Sign Out."
Sign in with the alternate account.