It means, unzip it in your orbiter install folder by using a unzipping program.
"Directory structure" is the way the install folder is build. So: "Config, Doc, Flights.."etc.
It means:
- Install 7-zip (exe version)
- Put the Cessna addon in Orbiter root folder
- Righ-click on the addon and select "7-Zip..." -> "Extract here"
- Answer "yes" to the overwrite warnings
And depending on which Cessna It may not work. Because of version of orbiter it was made for. This one:[ame="http://orbithangar.com/searchid.php?ID=3249"]http://orbithangar.com/searchid.php?ID=3249[/ame]
has the code so it could be updated