Lovely, lovely little plugin, but forum appears to have been abandoned.
We're meant to press a little downwards arrow icon to the right of the media uploader, which triggers a popup dialogue box. Entering text in that however (no formatting options available, WordPress 3.5) outputs a string of unformatted text, so forget that.
Instead, format the part of the post you want to reveal/hide as per normal posts, then manually place [EXPAND whatever] [/EXPAND] around that block of text. The 'whatever' can be any characters at all (presumably) and simply acts as an identifier for that block of text. Therefore we can have multiple sliders:
My list will be revealed
My pictures will be revealed
Tested in WP 3.5 and Chrome, Safari, Opera, IE and FF, worked in all of them.