When navigating to the user roles tab in Settings / Users, you'll have an overview of all available AppsCo HR roles.
Click on See employees on a role to view all employees, add and remove the employees with the assigned role.
A modal will open on the right which will allow you to add, remove and view all leaders in your company.
Click on the Assign role field to add or remove leaders and click on Save to save the changes. The list will be updated immediately and the selected users will be assigned or have the role removed from their user.