Hi Abhishek,
This process is described in the help. Please see:
Scheduler Administration http://help.sap.com/saphelp_spm30/helpdata/en/5f/e7f49df96d42caa8342c1b9e33b026/content.htm?frameset=/en/55/65b682056940d2aadc1f10587e889b/frameset.htm¤t_toc=/en/2c/6dd68a591a4f1aba2129b8013632d8/plain.htm&node_id=32
Creating and Modifying Alerts
http://help.sap.com/saphelp_spm30/helpdata/en/73/4cceafd1f846ccab56fbd1f2b5127a/content.htm
Kind Regards,
John