Follow this link:
1-://www.irctc.co.in/beta_htmls/etktcanc.html (in first para of the guidline, you get hyperlink under 'HERE' in blue letter and you get following link.
2-://www.irctc.co.in/beta_htmls/eticketguides.html
A short excerps of guidelines on CANCELLATION OF...
more... e-TICKET - A GUIDE
If user wishes to cancel his e-ticket from 'BOOKED TICKETS' link on the left navigation bar, select the ticket to be cancelled and click on 'Cancel e-ticket' and can initiate the cancellation by selecting the passengers to be cancelled.
For full you have to go to link and study in detail what is says. It is very simple
Hope this should get you going.