Quit CS5. Look for the installed CS6 on your disk and launch that application instead.
Adobe upgrades are FULL INSTALLERS, they don't touch any prior version(s) you may have installed. They install a new application.
CS6 installer will not automatically install a desktop shortcut. You must do this.
In Windows, click on the Start button, type Photoshop CS6 in the search window and it should show up.
In Mac, do the same in Spotlight.