To install this update scenery, you must delete or deactivate the previous willow fire scenery. This update shows the fire as almost out, and if you don't delete or inactivate the previous scenery, then you will still see the whole fire.

These instructions assume a default installation of FS9. If you have installed your sim to a custom location, you will have to locate the appropriate folders within your install.

Copy the Willow2 main folder to wherever you place your downloaded scenery. If this is your first scenery installation, then I suggest the C:\Program Files\Microsoft Games\Flight Simulator 9\Addon Scenery folder. Make sure the scenery and texture folders are inside the main Willow_Fire folder, with no cover folder over it.  
Copy the effects into your C:\Program Files\Microsoft Games\Flight Simulator 9\Effects folder.
Start FS.
Click Settings.
Click Scenery Library.
Click Add Area.
Browse to where you placed the Willow2 folder, and click on it. If for some reason it does not automatically, name the scenery Willow_Fire_Update.
Click ok.
Shut down FS and restart it.