You can upload it through your cPanel. www.yourdomain.com/cpanel and just use your username and password that you get once you sign up
You can FTP it. You will automatically get a FTP when you sign up and can add more if you need from your cPanel
If you have your site with another host and that host also runs cPanel, we can transfer it in for you pretty easily. Once you sign up you would fill out a support ticket in your client area, and we would just need you cPanel login for your other host.