In order to swap internal memory with SD card for installing apps, you need to ger Developer Preview update Windows Phone 8.1 .
This is the update that goes with Cortana ( voice assistant for US region).
After you update to WP 8.1, you will have an option in Settings - where to store music, downloads and APPS - on external or internal memory.
Google " windows phone developer preview how to "
The update is easy to install and gives many nice features