If you are new to the Android and want to test and develop applications you need to install Android SDK tool integrated with Eclipse editor.
As first step you need to download the SDK for your computer. Select the SDK for you operating system.
Download the Android SDK
Windows: android-sdk_r15-windows.zip
Mac OS X (intel): android-sdk_r15-macosx.zip
Linux (i386): android-sdk_r15-linux.tgz