Thanks so much for your response!
With respect to placement, I see how this works, and am a little embarrassed that I didn't see the parameters.
With respect to the first point, I've tried placing the css code in the “Custom CSS” box under Theme Options. When I “save”, the code disappears. Is that expected? And the appearance of the icon has not changed (the width remains narrow, and the search button text does not appear.
Note that the Display Search Text Button has been set to ON, and the search button text does appear beside the icon when the icon is clicked.
Am I misinterpreting your instructions?