You can go to the following website http(s)://[DMA]/tools, where [DMA] is the hostname of your DMA. There you can download the latest version of the Alerter tool.
You then have to exit the current version of the Alerter tool and install the new .msi app. All the configuration is kept, so you don't have to do anything for that.
If you want to be sure and have a backup of your configuration you can go to %APPDATA%\Roaming\Skyline\DataMiner\SLAlerter. There you can find the .xml file of your settings. You can take a copy of this to have a backup to be sure.