Go to Domains -> Web and edit the subdomain.
Make sure it is fully hosted. Choose your friend's FTP user for "All CGI should run as user:"
Then make a note of "Web Directory" below that:
Web Directory: /home/cgiuserabove/[something]
This means if the FTP user is "mithrandir", and the subdomain is "isengard", and your domain is "example.com", then the Web Directory will by default be:
/home/mithrandir = FTP user home directory ( "/" in FTP)
/home/mithrandir/isengard.example.com = subdirectory of home directory where web server looks for web files.
So write down what the home directory and web directory are, and save the changes to this panel. Then log in as the FTP user. If you don't see the web directory, you need to create it. Then upload the web files into that directory. CGI scripts may need to be configured to use the home directory or web directory that you wrote down.
Perl / MySQL / HTML+CSS