I press the add chapter button

This pops up. If the image doesn't show, there's a box with the word editor and an x. But I can't click out of it.
Seemingly no way to get past it and it makes a ringing noise. I just want to add new chapters one at a time.

 Which button are you talking about? There are several ways to create a chapter.
Which image are you talking about?

Under "New" the chapter icon. I get the same result when I use the keys ctrl shift c.

Sorry, I can't reproduce what is happening to you. The beep certainly indicates that you are in a dialog box and that you need to exit it first. What is the "x" you are talking about? Is that the traditional symbol for exiting a window?