First your website needs to be configured to use the SSL certificate. That is the responsibility of your hosting company. Once they have it configured they can tell you what the secure path to the shopping cart cgis, backoffice cgis, your media directory and the directory where the ShopSite images are located.
Once you know that information you configure the setting in ShopSite under Preferences > Hosting Services. The help for that page (or any backoffice screen) can be found by clicking the red ? button. The 9.0 help page is at
http://shopsite.com/help/9.0/en-US/sc/p ... rvice.html .
Note: Occasionally some hosting providers do not provide access to this configuration screen so you would need to contact them to make the required changes.