The text IN the box is what it will be called. To actually make the spoiler, you have to type stuff in between the [ Spoiler ]Typing stuff in between[ / Spoiler ] (And remember, those tags have no spaces.
Trying again: As before, there is a bracketed thing that shows up (inserting spaces to mess up the code so you can see it) [ SPOILER="THRICE"][/SPOILER ]
But I'll bet it doesn't show up again ... how about YOU post a spoiler alert and I'll tell you if I can see it?
YUP - it's still not there in my message. Where is it supposed to show up, anyway?
Ah, OK - it's the spoiler BUTTON that's not working then. I used the spoiler button, and what showed up in my message the way I showed you, with the = sign (and minus the extra spaces I put in so you could see the code. What I typed into the spoiler box did not appear at all.
I used the button, and (minus the spaces) this is what it looks like as I'm typing my post:
[ SPOILER="This is the text that I'm HIDING"][/SPOILER ]
Now, I'll redo what the button inserted into my typing box, but I'll delete the = and the quote marks, and move the ] to right after the word SPOILER instead of after the text, (and change the text a little):