My IPad mini says my Apple id has seen disabled. How do i enable it?

Depending on why it's been disabled you might be able to re-enable it via this page : http://appleid.apple.com, then 'reset your password'

Or you might need to contact Apple : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page

If it then works on your computer's iTunes but not your iPad then try logging out of your account on the iPad by tapping on your id in Settings > iTunes & App Stores and then log back in and see if that 'refreshes' the account on it