You can edit an existing alert policy and its components by displaying the desired values in the details pane and changing them.
To edit an existing alert policy
In the navigation pane, expand the Alert Policies node until you can view the item you wish to edit.
In the display pane, click the item(s) you want to edit.
Make the desired changes in the details pane. Any changes you make appear in bold until you save them.
Save your changes.