Christina. I’m not from Theme Horse :-), but when I logged in the download was on my account page—and that download had the style sheet.
I simply unzipped it (it had the style sheet). Renamed the file Interface 1-08. Zipped it back up and then uploaded it (as an add theme in the themes dashboard) and it worked perfectly.
Changed the active theme to the 1-08 and deleted the 1.07 version. The only change I had to make was to select the menu again. Everything else worked like clockwork.
Hope that helps,
B