Or, as I said before, there are many extensions which produce gcode, and I don't really know if one or another would work better with your particular setup or hardware. So if you have specific questions, hopefully someone else can help. The various options in those dialogs are not necessarily clear or easy to understand, at least not for me. If that tab is not open when you click Apply, you won't get a gcode file.)

Either Extensions menu > Gcodetools > Engraving, or Path to Gcode, whichever one suits your needs best (This creates the NGC file.) (Note that when you click Apply button, you need to have the Preferences tab of that dialog open.

Extensions menu > Gcodetools > Tools Library (This adds additional text to the green box.).

Extensions menu > Gcodetools > Orientation Points (This will put some points with some text, and a green box with some text, on the canvas.).

Is there some reason you decided to install it? Is your hardware meant to work with it? Possibly that's why it's not working? Although that's just a might be broken anyway. I have the impression it's meant to be used with makerbot unicorn hardware, though.

But I can't help at all with the makerbot unicorn extension. Since I know the basics for using Gcodetools extensions, I can give you the general steps.

As far as I know, they won't work together, and are not interchangeable. You need to settle on one extension (or set of extensions) or another.

Makerbot unicorn gcode download