Android Studio uses Gradle for building. Version 2.2 should pick up all
libraries specified in build.gradle file. However, If you change anything
in Project Structure dialog it won't update build.gradle file.
This file should NOT be empty. There is another empty build.gradle in
the project_root folder so do not confuse them. Add all libraries you need
inside dependencies closure. Do not confuse dependencies closure with
apply plugin: 'android'
//here is depenency from Maven Central Repository
//here is dependency from your local libs folder