Deactivating Timesheets is an Administrative permission. If you are supposed to have permissions to do this but you do not, then please contact your system admin.
Click the Recruit focus in the left menu panel > click Admin
Click Timesheets > find the timesheet that you want to change
Click Deactivate
Choose a Status
Click Deactivate
You will now see the Timesheet has been made Inactive and the Status has been changed to Cancelled.