I successfully downloaded Mavericks, but it did not install

I downloaded Mavericks into a two or three year old MacBook running osx 10.8.5. Installation never started. It took me through the acceptence of terms and conditions and I pressed "Install", but nothing happened except it may have triggered a time machine update. Now when I go to the software update page it shows that the update has been downloaded, but I can't find it on the computer in the downloads file. Where is it? How can I either get the installation started or reboot the process with a new download?