You must create an FTP account in your Cpanel and then start using it.
Most probably its automatically created you have to type your site name that is
Syntax: yourcpanelusername:yourpassword@yoursite.x10hostingdomainname.com in the first text box of filezilla or enter each in the seperate boxes provided.
for example: demouser:sec_pass@mango.elementfx.com:21 .
Welcome to X10.
Welcome to x10 erhlich! In an FTP client, the FTP adddress is your site address and your cPanel username and password. You can additionally in cPanel make an FTP account as stated above to have your FTP password different from your cPanel password.