These instructions assume you have Repository Level Admin Access AND Cabinet Level Admin access for NetDocuments
From The Cabinet Administration Page locate the Cabinet Security Section as shown here
Note you may need to click on 'ALL GROUPS' in the right hand side to show all groups
Add the EXTERNAL GROUP to the Cabinet from the ACTION COLUMN
MAKE SURE YOU SELECT 'NO DEFAULT ACCESS'
VERY IMPORTANT 'NO DEFAULT ACCESS' IS GIVEN AT THIS POINT
This means what this means is that the group HAS NO access to any content but is available to be added to the content.
If you chose any other option you have just given full access to every item in the ND System
No DEFAULT ACCESS is represented by a star as shown above