In the Company Profile option on the left menu, you will find the Work Week settings.

The standard Work Week of Monday to Friday will be set by default. To add a custom Work Week, click on the "Add new Work Week" button. 

You can select either Fixed Timing or Flexible Timing. 

A Fixed Timing Work Week will mean that Start of Work Time and End of Work Time are set at a fixed time. 

A Flexible Timing Work Week will mean that Start of Work Time and End of Work Time are not set at a fixed time. Employees are instead required to complete a fixed number of working hours on their working days.

You can apply the Work Week as a default for all employees or to particular employees.

Once you've created a new Work Week, you can choose to apply it to ALL Employees by changing the Default Work Week Settings under Company Settings. 

Note: This will only apply to employees who are under the default settings (i.e. their Work Week has not been changed individually). 

If you wish to only apply this Work Week to particular employees, you can go to their individual profiles to change their settings. 

Go to My Employees > Employment and under Working Hours And Public Holidays edit the "Work Week applied".