It would help if you specify what version of Teamcenter & Active Workspace you are on.
In Tc 11.2.2/AW 3.2 - Navigate to Item then to Item Revision. If there are sub-assemblies/components, it should automatically go to "Content" view. Alternatively, you can click on "Content" button to see the structure. If there are no parts underneath, it will present Add Elements panel on right side to allow you to add components.
As far as I know you have to install the Base Install -> Active Workspace -> Client -> Active Content feature from TEM, and you might have to do some configuration in BMIDE as well. Eventually check the AWC configuration manual.