The default storage will always be the phone memory. You can just move the apps after it gets installed. But please note that not all apps can be moved. Those apps are meant to stay in the phone memory. If in some way you move it, it will not work properly and could cause the app to crash.

To move app, go to Settings > Application Manager. Search for app and tap on it. If the 'Move to SD card' is available that means you can move it to external storage.