If your clock in setting isn't enabled, both Admins and employees themselves can enter timesheets hours.
If an employee notifies you that they can't enter any timesheet options, whether it's because they have no timesheets option or the start, finish and break fields can't be clicked, make the checks listed below.
Check the employee is in a timesheet group
An employee doesn't have access to timesheets unless they've been assigned to a timesheets group.
You can check if the employee is in a timesheets group by clicking on the number next to the group in the Employees column.
This will then list every employee in that group.
If you click on the number next to Employees without timesheets you will see every employee listed who isn't yet assigned to a timesheet group.
Check if 'Clock in' feature is enabled
If your clock in feature is enabled, this means timesheets can't be entered manually. For an employee, the dropdown fields will show as greyed out and not be able to be clicked on like in the screenshot below.
Click your name in the top right, then click Settings
On the settings menu click Timesheets, then click Time clocking.
Check to see if Enable time clock is switched on.