Hosting Subdomains

[equestrian-]

Alright, I recently bought my own domain name, lets call it mysite.com. I want to host other sites as subdomains.. so subdomain.mysite.com

I had no trouble setting up subdomain.mysite.com with my host but on my FTP server I am not sure how to limit my hostee's access. In other words I am not sure how to give them their own FTP username and password so they can access thier site and not mine.

I added a 'runftp.txt' file to their account. The information on the document says:

     open "dns1.domain.com/132.06.24.547"
     "%username%"
     "password"
     cd /upload
     bin
     hash
     put/get "filename.cab"
     bye

But the username and password that I put on aren't working and inorder to make the connection I have to use my own. But then my everything for my site comes up too.

How can I host a subdomain and only give them access to their part of my site???