first you connect your phone to PC .Then you can see three options in your phone.
1) file transfer
2) phone mode
you select phone mode. then SONY ERICSSON pc suit will launch in your PC. select internet connection in tools.then the connection wizard will appear.the same time you call BSNL CUSTOMER CARE and select GPRS SUPPORT CENTRE. They gave the deatails. keep 50 rs Minimum balance for using BSNL GPRS.