This is the way I just did on Android Studio version 1.0.2
- I have created a folder libs in [your project dir]\app\src
- I have copied the jtwitter.jar (or the yambaclientlib.jar) into the [your project dir]\app\src\libs directory
- The following the menu path: File -> Project Structure -> Dependencies -> Add -> File Dependency, Android Studio opens a dialog box where you can drag&drop the jar library. Then I clicked the OK button.
At this point Gradle will rebuild the project importing the library and resolving the dependencies.