how to set up build.gradle in eclipse

I am following the Thingworx Extension Development User Guide.pdf.

This guide suggest to use STS Gradle but I couldn't find that plugin. (Customer security doesn't allow to browse net marketplace in eclipse) 

also my Eclipse(version Oxygen.3) has Build.gradle plugin and this plugin doesn't work properly (It needed to be set up configuration). 

please guide me to set up gradle. ( where I could download STS Gradle plugin.zip)  

or how to use Build.gradle