Select the icon for the application installer on your Android mobile device. Application installers are available in the Android Marketplace, and through the main menu of your device. AppInstaller, Astro File Manager and APK Installer are three examples of programs that can work with .apk files.
Select the "Install" option in the application installer that you are using (if applicable).
Select the icon for the .apk file you want to install. Select the icon file for your SD card first (if the .apk file is stored on the SD card). Select the "Run" option within your application installer to run the .apk file and install the associated program.