well just connect your system with a LAN cable to the switch. The BSNL router will manage rest on its own.
Just keep the setting in your network connection settings in Internet Protocol(TCP/IP) as "Obtain IP automatically" and "Obtain DNS Server automatically.
Nothing to be done with switch but with broadband.
I hope your modem is set as the IP 192.168.1.1
As pimpom suggested your computer names should be unique.
This whole above is a step when your Broadband is already configured and you can use it on a single system connecting directly through LAN cord to the modem. If not then You need to get your broadband working on one system connecting directly to the modem.
A working broadband means that you have activated the BSNL broadband facility using the user name and password. This was doen for me by the BSNL person who had come to give the modem at my place. Better they do it for you. Because they will also confirm from there place if the have got your broadband activated or not. Call into exchange and get it done. if you do not know then you can register a complaint online on BSNL site. Broadband and modem not working.
If not then you have to work a little and first configure your modem.
This whole process has been explained previously. I am not searching it for you, do it your self. But in short this is done by opening
http://192.168.1.1 and configuring it.