When you connect to your Mezzmo library from a web browser, you must first log into your user account so you can access the Mezzmo library.
User accounts are created and managed in the Web Access dialog in Mezzmo Windows. They let you control who is able to access your Mezzmo library and what folder, playlists and files they are able to see. You can even create personalized homepages for each user account on the User Settings dialog (Homepage tab).