For biguglyhag and anyone else who was confused.
Okay, here’s what I did, step by step:

1: For some reason, I have two XKit icons on my Dash. Clickthe one that actually works. 😛
2: Then click Other. A new screen should pop up.

3: Scroll down to the bottom.
4: Click the Xkit Editor.

5: Click

A source code screen should open, that’s blank.
6: Click New Extension
7: Type in common into the text box, not noname; that’s just what I used as an example. Click OK.

The screen should fill up with a few lines of colorful text now.
8: Select all of the text, so it’s all greyed out.
9: DELETE EVERYTHING. It should go back to being blank again.

Right there at the top of your post was the link you need to click (I know; I overlooked it, too).
10: Right-click with your mouse, or hold down the [Ctrl] button and click it, so it opens in anew tab (if you’re on MS; I don’t know what a Mac does; they’re strange.)

You’ll get this page, FULL of colorful text.

11: Select ALL of the colorful text, and Copy it.
12: Go back to your blank code page and Paste all of it there.
13: Click Save.
And you’re done!