need help configuring Jenkins

[Rick Hillegas]

I don't seem to know how to configure the Jenkins trunk build to use 
Java 9. I tried adjusting the Tool Environment section, but that had no 
effect. In the Build Environment tab I see a dropdown for specifying the 
Ant version. But I don't see a dropdown for specifying the JDK version. 
My casual googling turns up responses which don't correspond to the 
layout of our Jenkins tabs.

Does anyone know how to do this?
Thanks,

-Rick