Hi Charlotte,
Your wireless router should have a port (socket) for an RJ11 modem lead to go in the back. It's this small cable with square blocks at the end that will connect into both the ADSL filter and the back (normally) of the router.
When I switched from a BT Voyager USB modem to a wireless router, I nicked that black lead out of the modem (it's no use in there any more) and put it into my router.
Let us know if that helps
