Add Scene Builder to Netbeans 8.2
Here are the steps that I went through to setup Scene Builder:
You can download Scene Builder 8.2 here
 
Install the package (or run the installer) and find the install location
/opt/SceneBuilder on Ubuntu 
C:\Users\{username}\AppData\Roaming\Scene Builder on Windows 10 
 
Then to link it to Netbeans IDE 8.2 go to Tools>Options>Java>JavaFX
 
Select Browse from the  Scene Builder Home drop down menu
 
Finally navigate to the install location for Scene Builder 8.2 and click Open and then Ok
 
To enjoy your newly found Scene Builder bliss, right click on a .fxml file in the Project Pane, and select Open. 
[Note: One would use the Edit option to edit the .fxml code ]
[Update: You can still download Oracle's JavaFX Scene Builder 2.0 here, but Gluon is now maintaining Scene Builder ]