When 'Mandatory Agency Approval' for timesheet is ON (Settings >> Settings), the timesheets can only be sent to the clients for approval after it's been approved by the agency.
When the setting is ON, the Agency column will appear on the All Timesheets page. To review/edit/delete the timesheets as the Agency, click on the Click here to view button.
The view, edit, delete and approve timesheets icons are present against each timesheet.
You can also 'Select All' timesheets or choose & select multiple timesheets to approve.
Click on the Tick to approve the selected timesheets.
After approving the timesheets, click on the Finish button to get back to the All Timesheets page.