The Agenda strategy on mobile can be accessed through the Sidebar or through the Bottom menu. To add it there, open the Sidebar, tap on "Account Settings", and then on "Settings". In the Settings, you will find options for customizing the sidebar/bottom menu.
To add Agenda, click on the "plus" icon on the top-right. For "Type" choose "Internal Link" and then choose "Agenda".
By default, your Agenda will display tasks, events, time blocks, and habits but you can configure this by clicking on the ⋮ icon on the top-right.
To create a new task, event, or a time block just tap at the time you want to schedule it for. At the moment it's not possible to drag existing tasks into Agenda or to move them for a different time by dragging and dropping them.