You can manage users membership yourself in collections.
Navigate to the collection you want to manage from omniContent \ Collections, select Manage next to the collection from the drop down option menu.
Select Members section to see a list of members and manage their security.
- Click Add Member to add an existing user to collection.
- Click X next to the member to delete him from a collection.
- To turn on/off specific permission for that member, select Permission and turn it on/off.