1. Install GAE - Netbeans Plugin
Download Google App Engine Netbeans Integration plugin from from the below link
https://code.google.com/p/nb-gaelyk-plugin/downloads/list
Extract the contents to a folder.
Now open Netbeans IDE and go to Tools -> Plugins
In Downloads Tab, click Add Plugins and browse to the folder which contains the extracted files of the GAE Plugin and import all.