How can I install apps on my Android SD card?

David got a new LG phone and now he can't put apps on his miniSD card. He could on his old HTC One, though. Leo says that LG may be preventing app installations on it. Or, it could be a function of the app that prohibits it. If it's a widget, then it can't. Also, that phone may not support it from LG's point of view. David can root the phone, though. CyanogenMod will do it.