Go to Calendar View > Swipe to the left to unfold the Arrange Tasks. Tasks that haven’t been given any due dates will be displayed here.
If you want to arrange certain tasks only, e.g. work-related tasks. You can tap Filter Lists on the bottom and make your selections.
Once you‘re ready to start arranging, long press on a task and drag it onto the calendar, drop to put it into any time blocks.
If you want to cancel the current action, drag & drop the task onto the "x" area on the bottom right corner.
When you are done, simply swipe to the right to fold Arrange Tasks and you’ll be back to normal Calendar View.