As you might know Gradle is a build tool like Ant and Maven (only it is better :)). If you don't already know Gradle, you should visit http://www.gradle.org as they have a vast amount of (good) documentation. For the rest of this documentation, I will assume that you are somewhat familiar with Gradle.
This plugin will let you open Java based Gradle projects in NetBeans. To begin using this plugin, read the Getting Started guide.
If you plan to build the project from the sources or you want to make some adjustment, read more on the development page.