Departments are used to group individuals that can perform specific work against a number of service categories (ex: Property Mgmt., Building Services, etc.), based on their permissions given and location(s) assigned. 

By adding departments, you can assign any work order to a department and then any internal vendor assigned to that department can “Accept” the work order, which then becomes their “Assigned” work order to complete.

To add a Department(s), go to Settings>Advanced>Departments, and choose "Add New Department" (see below). 
If your org is using the condensed version, go to Settings>Basic>Departmentsand select "Add New Department".

You will be redirected to a new screen where you can add your department and associate it with one or multiple service categories (see below), then SAVE. You can continue adding departments by repeating the process.