Hope this is useful.
To hide a portion of your post requiring the user to click a button to view that portion, use the spoiler bbcode
So, (without the space after [)
ENCODED_BBCODES_REPLACEMENTSspoiler]This is hidden
To change the text of the button, simply add =BUTTON_VALUE after spoiler. So.....
ENCODED_BBCODES_REPLACEMENTSspoiler=I love this forum]hidden text/image etc goes here