In the Planning Layer, select Planning Search on the left and enter your search criteria. Once you have selected your necessary filters, click the bell and you're subscribed to planning alerts for any updates related to that search.
You can manage your alerts in the Dashboard area or in the panel where you created it.
TIP: Only users on the unlimited plan can create as many as they like. Pro users get 1 alert that is restricted to a 0.25-4km2 area.