Nostalrius Begins - Quality wow vanilla realm (1.12)

I've just recently started playing, and I'm an avid keybinder. I've correctly installed Bartinder, my select bar addon, but it does not plug in correctly or something along those lines. So I'm just wondering where can I find the "bar" or "button" of that little special spot stealth lies in, to keybind it? I appreciate any help given, thanks in advance guys.

I don't know the exact name of the bar, if it has one, but you could also drag the stealth button out of your spellbook (P) to any other button on the bar - unless that was not possible back in that version.

most likely there is no way to bind it directly but correct me if I'm wrong, but the alternative mentioned above is the easiest and common way to deal with binding stealth/stances/shapeshift buttons.
pick a spot on your actionbars, drag the spell on it and bind it. I'd suggest hiding the original Stealth/Stance Buttons after doing so, so that you don't have those spells multiple times visible.
Tip: you can also do that with a "hidden bar", keybinds do work on bars which are hidden.

I use bartender2 as well, you can bind the stealth bar in the keybinds options in the menu. I think it's called something like "Special ActionBar" but I'm at work and can't check at the moment.

Special Action Button 1 is the Stealth bar.