First click on the desired task. From there you can set a date, a time, and an alarm for your task by clicking on the date and time to the left of the reminder icon . When finished click 'OK'. On a shared task, when you change the task time, the other members will see the same time but each one can decide to be reminded or not on the due time. Alerts for individual tasks can be toggled ON or OFF by clicking on the task to see the task options and then clicking on the bell icon.