If you want to add Shopping Cart, Email Marketer and Knowledge Manager to an existing site then here is an example directory layout assuming that when you ftp in to your web host all your website files are in a httpdocs directory
httpdocs
httpdocs/shop <- This is the Shopping Cart base directory
httpdocs/shop/admin <- This is the Shopping Cart control panel directory
httpdocs/newsletter <- This is the Email Marketer base directory
httpdocs/newsletter/admin <- This is the Email Marketer control panel directory
httpdocs/support <- This is the Knowledge Manager base directory
httpdocs/support/admin <- This is the Knowledge Manager control panel directory.
This obviously assumes you want the directories named shop, newsletter and support. These could in fact be anything but it is best to keep them to a simple name without any special characters and all lower case letters in most cases.
If you wanted Shopping Cart to be the home page for your site and wanted Email Marketer and Knowledge Manager to be installed under that, still assuming that all your website files are under the httpdocs directory, the structure might look something like this
httpdocs <- This is the Shopping Cart base directory
httpdocs/admin <- This is the Shopping Cart control panel directory
httpdocs/newsletter <- This is the Email Marketer base directory
httpdocs/newsletter/admin <- This is the Email Marketer control panel directory
httpdocs/support <- This is the Knowledge Manager base directory
httpdocs/support/admin <- This is the Knowledge Manager control panel directory.