To open the personal calendar, click on the My tasks button in your left side menu under the My work section and choose Calendar on the top navigation menu.
By default, the calendar opens on the monthly view, displaying the tasks with due dates of tasks assigned to you and incomplete.
The color of the circle next to the task labels represents the first shared subject of the task. So if your task is shared on a subject that has a red color, the task in the calendar will reflect that by displaying the red color as well.
If you are not familiar with the Azendoo calendar basics, learn more here.