These instructions refer to a very old version.
What kind of toolbar are you missing? Do you have in mind specific buttons or functionality?
The only other bar you can enable in the settings (under user interface) is the bookmarks bar.
Sincerely, I wouldn't go all the way back to Opera 12.17 for toolbars - I can't recommend it, it's simply too slow/laggy/incompatible with the today's web. Stay in the current Opera version or choose another browser that suits your needs better. Tell us what specific functionality you miss and we might be able to help you access the functionality, point to a keyboard shortcut, setting or extension.