how to include jar in cuba studio

I need to use few utility jars in my project. I tried to learn from link https://www.cuba-platform.com/discuss/t/cant-use-my-jar-file
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,
Thanks

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