I know this should be simple but please can somebody explain very quickly where the modem goes in all of this:

Broadband provided via talk talk (phone line).
USB Modem, came with Talk Talk
Linksys wireless router
PC with no ethernet point on it
PC has a wireless card in it
also connecting an xbox via ethernet

i thought that i connect the internet connection to the router and then connect the router to the pc wirelessly. However, in order to configure the router i'd need to connect it to the pc but it has no ethernet - do i need an adaptor for ethernet-to-usb, as i had one once from an old ISP (NTL).
Second point, where does the modem go as it is a usb device and so cannot plug into the router directly?

THANKS