Um... How do I use spoilers?

You hit the "Insert" button and choose "Spoiler". You can choose if you want to name it or not, then hit Continue. To get text/images inside the spoiler post them in between the brackets -> ][, ]Like this[

 

When your typing above there is a bar. (The bar includes Bold, Underline, Italicized, etc.)
There is an Icon 3 places over from the smile button. Click the icon that looks like a piece of paper with an I under it.
Quote, Spoiler, Code, and Strike Through options are here. Click Spoliers. Enter Spoilers title. Type something or paste pictures, links, pictures, etc in between the first spoiler and the second spoiler. You could also type [/SPOILER] and end with [/SPOILER] if needed. After the first [/SPOILER] you can type [/SPOILER] with a = sign the title between the apostrophes like so:

Spoiler: Enter Spoiler Title

Hope this helped!
EDIT: When I refreshed the page I saw that this had been answered! @SupersonicE9