Installing Android Studio
Android Studio provides everything you need to start developing apps for Android, including the Android Studio IDE and the Android SDK tools.
If you didn't download Android Studio, go download Android Studio now, or switch to the stand-alone SDK Tools install instructions.
Before you set up Android Studio, be sure you have installed JDK 6 or higher (the JRE alone is not sufficient)—JDK 7 is required when developing for Android 5.0 and higher. To check if you have JDK installed (and which version), open a terminal and type javac -version. If the JDK is not available or the version is lower than 6, go download JDK.
To set up Android Studio on Windows:
Launch the .exe file you just downloaded. Follow the setup wizard to install Android Studio and any necessary SDK tools. On some Windows systems, the launcher script does not find where Java is installed. If you encounter this problem, you need to set an environment variable indicating the correct location. Select Start menu > Computer > System Properties > Advanced System Properties. Then open Advanced tab > Environment Variables and add a new system variable JAVA_HOME that points to your JDK folder, for example C:\Program Files\Java\jdk1.7.0_21. The individual tools and other SDK packages are saved outside the Android Studio application directory. If you need to access the tools directly, use a terminal to navigate to the location where they are installed. For example:
Android Studio is now ready and loaded with the Android developer tools, but there are still a couple packages you should add to make your Android SDK complete.