A timesheets admin is a unique employee who can see and do everything related to any employee who has timesheets. This user has access to the "Timesheets" tab in the Settings menu.
This person can manage Timesheet groups which therefore means they can add/edit employees and managers assigned to these groups.
Click your name in the top right, then click Settings.
On the settings menu click Timesheets, then click General.
Under Timesheet administrators, type the name for the employee(s) you want to be the timesheet administrator(s), click on the space, and browse to the relevant person.