How do I re-authorize my iPod Touch's Apps Store to a new iTunes Account?

I got a new iPod Touch a few weeks ago. I use a shared 13" Intel based MacBook Pro. My iPod Touch was initially set up on the administrator's iTunes account and i bought some apps on their iTunes account.

Yesterday we set up my own user account on the MacbookPro and my own iTunes Account/Apple ID.

I successfully re-authoirsed the computer and iTunes to my new iTunes Account/Apple ID and synced the iPod Toucvh to my iTunes.

However, while the computer is re-authoised, the iPod touch is not, and when I go to buy new apps from the Apps Store using my iPod Touch it only comes up with the old Apple ID/iTunes account. Going into Settings for the Apps Store on the iPod Touch only gives me the option to view the Apple ID/Itunes Account and no way to change it.

How do i reset the Apple ID on my iPod Touch so it is set to my new Apple ID and authorised to buy from my iTunes Account?