Assuming you have already set up a subject type, you can easily add these subjects to a case. To do so, navigate to the case, click the New button, and then select Subject.
From here, select the Subject Type from the menu and click Continue.
At this point you can enter the subject details and save the subject to the case. Repeat these steps to add as many subjects to a case as you like.
Note: If the Subject Type you are attempting to add does not show up in the list, this means it is not associated with the type of case you are working. At this point you should edit the subject type and make sure the appropriate case types are checked.