Notice you can fine-tune file access rights for each user: grant read-only rights (download only), write rights (to upload files), and whether or not the user can delete files or create directories, too.
If you want to grant several users access to your server all with the same rights and directory access, instead of creating each one individually, set up a user group. For example, if you're sharing your MP3 directory with friends, make a user group called "music fans" with access to the correct directory and add users to that group, which automatically gives them those rights. Then, if you move your music directory you only have to edit the group, not each user in it. To manage user groups, from the Edit menu, choose Groups.