Template missing Stylesheet

I am a newbie, just got WordPress and just bought a Template from Themeforest: Polyon. Attempted to install it 7 or 8 times and keep getting the same message.

polyon-modern-and-futuristic-html-template.zip.download Stylesheet is missing.

I have redownloaded the file 10 times from Themeforest.

OK I read 20 or so posts in the forum about this problem. The reason I have not done what the posts said is that I am SUCH a newbie that I don’t understand most of the lingo in order to do the right thing. Each post is different from the last, and I can’t seem to get the specific answer for my specific problem. Can anyone help?