The easiest way to accomplish this is to use the FTP account which is automatically created by cPanel.
- Login to cPanel and click FTP Accounts.
- Look for the account with Directory set to /public_html/addon (where addon is the name of your domain's folder)
- Use the corresponding password and username (the username resembles an email address, i.e. name@domain.com)
- If you forgot the password, use the Change Password button.
- When you are ready to publish, use the email-like username and password. Your files will upload to the correct website.