You can't. Android installs apps to internal storage. If you "move an app" to the SD card, it moves pieces of the app, leaving links in internal storage to each piece. Android was never written to look for apps on the card, it looks for them in internal app storage. If it finds a link to the card, that's where it tells Linux to load that code from. (Android never "knows" that the app isn't being stored internally.)
Even if you change the "installation location" to the card, it just installs internally, then gets "moved", the same as if you had moved it manually.
If you want your apps actually installed to the card, you'll have to find a ROM for your device that mounts the card as Android's storage. (Then the 4GB internal storage is ignored.)