When you signed up, you should've received an e-mail from Lunarpages regarding your account information.  Within that e-mail were the details for your FTP account (you can also get this from logging into your Control Panel).

Usually, it's something like:

ftp.yourdomain.com
username:  your cpanel user name
password:  your cpanel password

Hey,

This might be helpful.

https://support.lunarpages.com/knowledge_bases/article/195

Thank you