Login as admin on the Snow Leopard Server to begin. Then :
Launch Safari and download eZ, zip or tar.gz, does not matter. The "Downloads" folder will do it's little dance when the download is complete, open the download folder, double-click the downloaded file to extract it to a folder named same as the download file.
With the Downloads folder still open, open a second Finder window and browse from ServerHD or whatever the server primary disk is named, to Library->Webserver->Documents.
Drag the extracted folder from Downloads Folder into the Documents folder.
A couple of slow clicks on the text of the folder name will allow editing the name from ezpublish-4.3.xxx to ez43 or something short and descriptive to you.