To access departments click on the drop down beside your name and click 'Administration'.  Then click 'Departments'. 

All departments in your business area will appear here, you can add departments by clicking on 'New Department'.  You can also delete departments by clicking 'Remove'. 

These departments will appear within users details.  Departments are for workflow checklist to ensure the user gets the correct checklist when a generic workflow is sent out.  Departments are not compulsory it will just mean the user won't receive any checklists.