If more is involved than just an aircraft folder, there should be a text file with installation instructions. As DogFighter2111 says, unless you know exactly what the structure of the zipped file is, unzip it to a temporary folder and see if there's a text file with instructions. Winzip extracts to C:/Unzipped/-filename-/ by default. E.g. a file called Artichoke.zip would be extracted to the folder C:/Unzipped/Artichoke/ which Winzip will create (replace the slashes with backslashes - I can't get them to appear in the post).