Connect the modem directly to the Computer first and try n go online.If everything works fine then this is the no. for the Linksys Tech Support 1800-326-7114.
It's a toll free number call them and they will guide you step by step in a proper way.
Good luck.

Make sure that your computer is able to go online directly through the modem.
If your computer is able to go online through the modem, that means the modem is working fine.
You will need to connect the computer to the router and the modem to the router.
open the set up page of the router and change the settings of the router according to the ISP.

Click Here for more information about the routers and network