how to include jar in cuba studio

I need to use few utility jars in my project. I tried to learn from link Can't use my JAR file - CUBA.Platform
but didnt get it. as where to update Gradle:
buildscript {

repositories {
maven {

flatDir { dirs ‘c:\work\lib’ }

Can someone explain in detail steps to include custom jars

Please ignore , I found build.gradle under project directory,

Also you can use Project properties - Advanced tab from CUBA Studio.