On the left navigation menu, there is "Alerts Manager."
In "Alerts Manager", visit actions to modify the frequency of your ad alerts or delete any alert that is no longer relevant.
If you need to modify the criteria of your ad alert, you need to update your saved search in the Dashboard.
In the pop-up box, select Save As to update your current saved search with your new criteria. Your ad alert will automatically be updated with the new criteria.
Note: If you want to create a NEW saved search, enter a new name and select save.
To learn how to create an Ad Alert, go to this article
"How do I create an alert from the Dashboard."