Each Entity type may be broken into as many sub-types as necessary. Note that sub-types are always Site-scoped and can't be scoped to the Program level.
To create a new Entity Sub-type:
On the Navigation Bar, click "Entities".
Select "Define Entity Subtypes".
Select the Entity type you would like to create a sub-type for from the drop-down menu.
You will see a list of existing sub-types. Type in the name of the new sub-type you would like to add next to "Add New Sub-Type" textbox.
Click "Add New Sub-Type".
A pop up will appear notifying you of your success. You should be able to see the new sub-type in the list next to the "Existing Sub-Types:".
Click "OK" to clear away the pop up box.