adding ftp accounts

i wish to add ftp accounts to my site. it seemed simple until i read the following paragraph(s). i just want each user be able to upload and download specific to their username/ftp account, without giving them access to the other accounts/users. in plain english please.. help!

Directions:
If you enter a single / in the directory box, the new FTP user will have access to the entire public_html directory and all directories under it. If you just want the new user to be able to access a sub-domain, just set the directory box to the same value as the sub-domain's root name, which is listed in parenthesis on the sub-domain section of this control panel.

Please be aware that the new user will have read/write access to the directory you choose and every directory below it. For example, if you choose to add the user john, and give the user access to /home/dave/public_html/john directory, the user will be able to add, edit, rename and remove any file or directory in /home/dave/public_html/john.