In order to upload documents to be displayed in the meeting list widget, you must have at least one upload type created.
Go to the finalized meeting screen for the subject meeting.
The third tab is the Upload Center tab.
Click the Create an upload type button.
If there is already at least one upload type defined, the button will not be displayed. Click the Add another upload type link.
Enter an upload type label.
Click the Create Upload Type button.
The type is now available to choose as a type when you click the Upload a Document button.