In order to use the spoiler text feature text, this will happen when you actually make a post. When you get to the reply post window, it will look like this: (Font color selection has been clicked on)

When you type in the text you wish to make into spoiler text, you need to change the font color. First you highlight (drag across and over with your mouse) that text and then you then need to click on the large "A" at the top of the the box that has a color bar under it. This is the option of "Font color". A box of possible font colors will appear (see above). You then need to select the third to the last color from the right on the bottom row to change the color of the text you have highlighted:

Then you can finish your reply and click to post it. The font color is now the same as the background color and will be invisible until you scroll over it. As usual, you should warn in advance that Spoiler text is coming so people will know what the blank space in your post is about.

If you are replying to a post with Spoiler Text within it, and you are quoting it, that will reveal the spoiler text in the nested quote since its background color is different. It is requested that you simply highlight that quoted spoiler text in your reply, and then change the font color in the same exact way as above except that now you will use the second color from the right on the bottom row as shown:

This will change the color of the Spoiler text within the nested quote to its background color and keep it hidden unless scrolled over.