Everything in 360Player is shown for one group at a time. Switching group changes the calendar, the wall and the menu with it.
Open the group switcher — the control showing the name of the group you are currently in. It is in the app's header on mobile and in the navigation on the web.
Pick the group you want from the list.
The list is ordered: groups you belong to yourself, as a Player or as Staff, come first, and groups your connected children belong to come after them.
As a parent you have access to every group your child is in, without joining it yourself. If a group you expect is missing, you are probably not connected to that child yet — or not a member of the group. To join one, see Join a new group or club.