Clock-in Timesheet

Hello, first time creating an app. I am still learning about app creation. I want to create clock-in app and trying to modify the Timesheet sample app.

The clock-in/out action is linked to your email account as I understand. How can I change this to select the relevant employee?

We deliver a cleaning service and I want the client to clock-in/out the employee meaning client need to be able to select the employee who is on duty as it is not always the same employee.