I have FireFox-2 with Windows Vista, and to access Options, I click on Tools (near File, Edit and View on the tool bar). I don’t have an ‘S’ icon at the lower right.
Go to the “View” Menu and click on “status bar” so that a check mark appears next to it. You should now have a visible bar at the bottom of the screen, on which the NoScript icon will be located. I use Windows XP, but I’m assuming the behavior would be the same for both operating systems.