In this post you learn how to configure Wi-Fi on B.S.N.L ADSL router,modem
Same thing you can apply different ADSL modems & routers.After configured modem you can access internet on your wi fi enabled laptop,desktop,Iphone,mobiles.
Before you start you need to set your local ip to 192.168.1.3,Subnet mask 255.255.255.0 & Gateway 192.168.1.1