To password protect a download or download page:
1) View the download or download page you would like to password protect.
2) Click on the "Access Control" tab.
3) In the "View" column, check off the boxes corresponding to those users that should be allowed to see the upload. For example, unchecking "anonymous user" and checking "administrative user" will restrict access to users who have logged into the site.
4) Click "Submit"