Only users with proper permissions can enter the Site Management section to update a site's Qsheet profile. If you don't see the "Site Management" option (see below) on the left side menu when you navigate to Home > Administration section, then you need to get proper access from an existing system. System administrators automatically have access to this section.
This is a powerful page that lets users manage all aspects of a site's profile. You can easily add new sites/delete new sites and update all profile information, virtual tours and brochures. See snapshot below for a general orientation.