1. Install netbeans-jpf (see: Installing the NetBeans JPF plugin)
2. Make sure the correct site.properties file is being used for JPF (The default is usually correct)
3. To see which site.properties file is being used:
4. From the NetBeans top menu go to "Tools"->"Options" (Alt+T followed by Alt+O)
5. Select "Miscellaneous" from the top of the Options Window
6. Select the "Java Pathfinder" tab
7. Make sure that "Path to site.properties" is defined properly, uncheck "Use default site.properties location" to change the path
8. From either the "Projects" or "Files" view (on the left of the main NetBeans screen by default,) select the JPF properties file (i.e., a file with a .jpf extension) you would like to run. Right click on this file and select the "Verify..." menu item to run JPF.
9. To view the results, make sure that the "Output" View is open (On the bottom of the main NetBeans screen by default)