installing

You can read the Readme and it will tell you where to put the files.
Generally, you put the scenary files inside the Addon Scenary - scenary folder. The textures goes to the Addon scenary - textures folder.

Agus is right on. 👍

There are a number of way to install scenery depending on what it's supposed to show.
You have to go by the read-me or post it here if you can't figure it out.
The most common way I have below.
If you closely follow it step by step it works!

1. Extract the zip into your main FS2004 Addon Scenery folder, or into a temporary folder, and then move it there, which ever method you prefer.
I use the temp and drag and drop.

2. Start up FS2004 and when the welcome screen, or initial menu comes on, select settings, then click on Scenery Library, and Add Area. Find the Addon Scenery folder and open it, then find the XXXX folder and click on it. The name XXXX should now appear in the title window, then click OK. Then you will see XXXX at the top of your scenery library list, and click the OK tab at the bottom.

3. That's it! You must first exit FS2004, and when you restart it your scenery will be there. It is not necessary to use the Addon Scenery option to locate this scenery, simply go to the airport in FS.

Yeah. I got it. I also downloaded and installed more AI traffic. It's so much fun knowing how to do these things.

I had to install my Lisbon scenary in the main Scenary folder. That's what the Readme told me to do.
So, always read the Readme.

Yep. I agree with you there.