From the Site Management section select Departments
The current departments for that site will be listed.
To modify a department, select the pencil icon to the right of the department name.
From this screen you can edit the department name and add or remove members from the department list.
To add a member, select either Accounts or Users from the drop down, then select the required member from the second drop down list that appears. Press the green + to add them to the department.
To remove a member press the red x next to the appropriate member in the list.
Repeat until all the modifications have been made to this department, then press 
.
To delete a department, select the red x icon next to the department name on the department list page.
Check you are deleting the correct department and press Delete to confirm. If you do not wish to delete this department then press Cancel.