Apps can only run on an SD card, and have the card set as the direct download location for apps, if the device is running Android "Marshmallow". Any other versions and it won't work.
Certain apps will let you save to the card, but most will not direct download to a card. Like a photo app, in it's own settings, may have the option to set the SD card as the place to save.
Now if you are running "Marshmallow" and also the manufacturer hasn't restricted the use of the card in this manner (some do restrict it) then you can try the following instructions.
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...