1. First, download and install the Olivenbaum plugin for each Revit version. You can download it from the plugin's official website or a reliable download site.

2. Second, open Revit software, find Olivenbaum plug-in in "Plug-ins" or "Add-ins" and enable it.

3. Then, create your project file in Revit. In the project, select "Add-Decorative-Mountain of Olives" to use the plugin. You can add trees and vegetation to your project as needed.

4. Finally, if you need to use the plugin in another version of Revit, repeat the steps above to install and enable that version of the Olivenbaum plugin.