Once you've unzipped the file you download you'll find four different folders in which all of the sound files are located in WAV, MP3, AIFF and iPhone alert formats. Once you have them on your computer, you'll have to save them in the folder you want to have them in or assign them to the notifications you want these sounds to go with.
On the author’s website there are links to tutorials that show you how to easily assign sound files, a feat that is not overly complicated but which may warrant more help for some users.
Soothing Alerts is a complete sounds package that offers really good alternatives to the traditional Windows sounds. Plus, because it also comes with sounds for iPhone you can easily upload it onto your mobile phone.