How do I send a notification on alarms?

Hi,
for details on sending notifications, please see the Notifications section of the PRTG manual.
Best regards

I have notifications working now, at least for "down" events. Is there a way I can set a notification on CPU utilization above some threshold using Cisco System Health SNMP sensor, without having to set that notification on each of those sensors individually?

You can use the sensor channel settings to set error and warning limits for a certain channel. This can be done for multiple sensors using multi-edit. To apply a notification to several sensors you might create a library an then add the notification to the library itself as every included sensor will use the same.
Best regards

I have created a library of all ping sensors, but cannot see where I add the notification to the library. Can you tell me where that would be?

In the library overview you should see a tab called Notifications. There you can add the different triggers. Please not that this feature was only introduced in late PRTG 12 so if you are on a lower version a update might be required to use this feature.
Best regards

I discovered why I could not find the Notifications tab -- it does not appear when using the Enterprise Console, only when using Web access. I've added the notification to the library.

Thanks for letting us know. A developer ticket has been opened and the functionality should be available with one of the upcoming releases. Sorry for any inconvenience.