People with the 'External' permissions group can only see the assignments on which they are named.
Adding an external person to an assignment, so that they can see it, is done like this:
Switch to the info page on the assignment(1), Associates tab (2). Search for the user you want (3) and click to add them (4). If they have ‘External’ as their permission group they will now be able to see and use this assignment.
