The first user to sign up in flex.bi Enterprise will get the System Administration access rights. If you want to add the system administration rights for existing users, then find the user in System Administration / All Users page, edit it and select System admin checkbox. If a user is a system administrator then on the top right corner there will be System Administration menu visible.
A system administrator can access all Flex.bi accounts data as well as perform additional system administration tasks that are described below.