Wireless network

I have just purchased a new dimension 8300.

I want to connect my old pc via wireless adapters to the1Mbit ADSL connection and printer which are now hard wired into the new 8300.

I think it has a spare ethernet port. I did purchase a TrueMobile 2300 which i thought would work but clearly I think I need a wireless router.

Both use XP Pro and the old (ADVENT) pc does not have a network adapter, but does have USB.

Can some one list the items im likely to need.

Many thanks