Urgent: Help Me Please!

I have a site for a client that I have to finish today, before i go out of town. I have the site all ready to go, and ready to publish to the internet. So my client gives me her server info and how to access the website. It turns out that she bought this weird thing where you build the page online and it does all the publishing and everything. It won’t even let me change the html of each page, or upload my own file.

I need to know how I can access the site’s file structure and everything. I have the username and password and everything too.

Please help!

Thanks,
3dnirvana