From the sidebar, click on Org. Hierarchy> Departments. You'll see a list of the departments added to the company account.
Next to the department where you want to assign employees to, under the Action column, click on Assign/Unassign Employees. Two lists will show up: one for employees who are not assigned, and the other for employees who are assigned.
You can move employees from one list to another by clicking on the employee's name in the list.
Click the >> button to move all employees to the other list.
You can filter employees by workplaces, worktimes, job titles, departments, or teams. The filter will apply to both assigned and unassigned employees.
When you're done, click the save button to finish.