A prospect is considered unattached if they have been added into the system without being assigned a specific job. To manage unattached prospects, a user needs to be Job Admin or above, with the additional user-specific permission Can manage unattached prospects.
Assign 'Can manage unattached prospects' permission
Job Admin need to have the user-specific permission Can manage unattached prospects. This permission allows Job Admin to add prospects to jobs and convert the unattached prospects into candidates.
To assign this user-specific permission to a person, click the Configure icon 
on your navigation bar, then click Users on the left.
Select a user with Job Admin level permission.
Scroll down the user's page to the permissions box and add a check in the box next to 'Can manage unattached prospects.'
When finished, click Save.
Assign 'Can manage unattached prospects' permission in bulk
To assign the 'Can manage unattached prospects' permission to a group of users with the same permission level, click on the Configure icon on your navigation bar, then click Users on the left.
Filter the users list by a specific permission level type. You can also apply any additional filters to narrow down your list.
When you've finished narrowing down your list, click Bulk actions > Select all > Edited selected.
Click Edit user-specific permissions.
Select Turn all on in the same row as the permission 'Can manage unattached prospects.'
When finished, click Save permissions.
Filter for unattached prospects
To filter for unattached prospects, click the Candidates tab on your navigation bar.
Expand the Application type filter on the left and click Prospects only from the Type dropdown and add a check in the box next to Prospects on no jobs.
All unattached prospects will populate.