Open up your agendas by tapping on the second button on the sidebar (highlighted in blue)
To select the agenda in Tablet mode: Hold and slightly pull down.
To select the agenda with a keyboard/mouse: Right click
The option to share will now show on the top toolbar. Tap Share.
A pop up will appear confirming that you wish to share this Agenda with all users, then there will be a notification that the Agenda sharing request has been brought to the attention of the administrator.
If you are the administrator, you can now follow these steps: Sharing Agendas in Media Manager