Well there are two things you need to be able to run apps from the SD card. 1. Your phone needs to be running, or upgradable to, Android "Marshmallow" and 2. You need to have a phone that the manufacturer hasn't restricted the option to make the changes on that device. Which does happen. The instructions on how to do it are as follows...
How to turn external SD card into internal storage on "Marshmallow".
NOTE: Please be sure you start with a blank SD card. It needs to be blank because when the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device).
1. Go to device “Settings”, then select “Storage”.
2. Select your "SD Card", then tap the “three-dot menu“ (top-right), now select “Settings” from in there.
3. Now select “Format as internal”, and then “Erase & Format”.
4. Your SD Card will now be formatted as internal storage.
5. Reboot your phone.
NOTE: If you don't reboot the phone, many things may not work correctly, so make sure you do.