This is the application that we use to register, roster and communicate with our teams and parents. This application has a matching mobile app, which you can read about downloading here.
The SportsEngine household account owner must provide access to each child's team/schedule as they are in charge of who has access to the child's schedule. The account owner is the person / email that registered the child/children. The adding of a guardian can be done through the mobile app (via account on the bottom right of the app options) or on the desktop version of SE. Here are the instructions for desktop/laptop:
Coaches/Team Admins, from the App: