Well, once your'e in your public_html folder, upload the ZIP file by pressing upload to the place where you want the site to me (in this case, public_html). After, when you click on the ZIP file once and then click on extract at the top, this may be where your problem is. Make sure it is extracting to public_html, and then press OK. You won't need to save it in any other directory, as the extraction should build all of your folders for you if the ZIP file contains that data. After that, you should be all set.