Once installed, you'll see a button to the right of your URL bar. Just click it to hide all your open tabs at once. Click it again (it will have turned green) to restore the tabs. That easy.
If you'd rather use a keyboard shortcut, you can also set it up to work with F12.
PanicButton is great if you regularly visit pages you'd rather other people not know about. The perfect tool if you work with lots of curious people.