Click on Settings and go to Employees. You can now create users on the Add employee button. If employees are to have access to the system via smartphone app, it is important that their email is entered so that they can receive an invitation by email.
After all fields marked in red have been filled in, you can define the weekly or monthly working hours for the employee below and then click on Save & Invite in the lower right corner. If employees should only appear in the system without receiving access rights to the app, you can leave out the field for the user's email and click on Save at the bottom right.