1) Login to Web Host Manager (WHM)
2) Click on Account Functions
3) Click on Terminate Accounts
4) You shall a list of cPanel accounts. Tick the box for the cPanel account you wish to terminate before pressing Remove button.
5) Confirm the deletion by pressing "Yes, remove this account".
6) The server will now process the request and remove all the account data.
Remember, this is NOT recoverable. Once completed, you will see the removal report on the screen.