With the access rights you can protect your documents by setting the access rights in the detail view. On the document you can see who has access to the document.
When there is no lock, all users have access to the document.
Under "Manage access rights" you can view and edit all existing access rights.
To assign access rights to another user, click in the E-mail or Name field and select the person(s) from the list.
Under "Users" you can add more users for your company, who will then automatically be added to the list for selection of access rights.