Q: i bought itunes cards for christmas, but the store said i had yo authorize them or set them up online?

You don't need to do anything with them, as long as the shop assistant activated the cards properly then all that you (or your dad) will need to do is redeem them onto his account.

Redeeming a card : http://support.apple.com/kb/HT1574

If when you come to redeem them you find that they haven't been activated properly (they should have been) then you will need to try contacting iTunes Support (you will probably need to give them images of the front and back of the card, and possibly its receipt) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then iTunes Cards And Codes