The Overdue Milestones view lists important milestones slipped beyond the completion date. You can check the overdue milestones of the selected project from the Dashboard also.
Hover the mouse over the required overdue milestone, and then click Complete to complete the overdue milestone. The milestone is moved to Completed Milestones.
Click Reorder, and then drag and drop the milestones based on your priority and then click Save Order to save the new milestone order.