After you install osCommerce via the Members Control Panel, you will be presented with a link to your new store's catalog. Simply copy and paste the link into your website. This will allow your customers to view your store's catalog and purchase proucts from your website.
Alternatively you may access your store catalog by browsing to a URL similar to the following (where yourdomain.com is your domain name, memberid is the member username assigned to your account and installation_directory is where you chose to install Commerce Pro):
http://yourdomain.com/installation_directory/catalog/OR
http://memberid.netfirms.com/installation_directory/catalog/