First you need to open up your router configuration page, usually the URL is something like http://192.168.1.1/ (192 are teh LAN address), consult manual to see if this is indeed the address.
Then find out where to input the ISP login details. There will be a status page where you can see if the router is connected to ISP or not.
If that is all done, your laptop should pick up the new WiFI signal.
Edit: Connect router to PC with Lan cable first, then access the router configuration page mentioned.







