Savitar downloads as a disk image (.dmg) file.
Simply double-click the downloaded file and it will be unpacked as a folder called "Savitar 1.5 folder". Drag this folder to your Applications folder. Congrats, you've installed Savitar.
Savitar version 1.4 and later has a "Check for Update" menu item in the "Savitar" menu in the menu bar. Selecting this menu item will result in Savitar looking at the Heynow website to determine if a newer version of Savitar is available. If there is a newer version, Savitar will ask you if it can use your default web browser to download the update for you.
You can also manually check for new versions of Savitar by visiting Savitar's download web page at http://www.heynow.com/Savitar/download.html
Simply drag the Savitar 1.5 folder into your trash and you are done.