Go to the calendar view > Click the "..." button at the top right corner > Click "Arrange tasks". Tasks that haven’t been given any due dates will be displayed on the right hand.
If you want to arrange certain tasks only, for example: work-related tasks. You can click the filter below "Arrange tasks" and make your selections.
Once you‘re ready to start arranging, click on a task and drag it onto the calendar, release to set up a date.