From the sidebar, click on Company> Worktimes. You'll see the list of worktimes for the company account.
Next to the worktime you want to assign employees to, under the Action column, click on Assign/Unassign Employees. You'll see two lists: one for employees not assigned, and another for employees already assigned.
You can move employees from one list to the other by clicking their name.
Click the >> button to move all employees to the other list.
You can filter employees by workplaces, working hours, job titles, departments, or teams. Filters will apply to both assigned and unassigned employees.
When you're done, hit the save button to finish.