Since that phone comes with Android "JellyBean" and as far as I know is only upgradable to "Lollipop". You would not be able to do this. Why? Because it requires you be running "Marshmallow" to make it work.
Now if you can somehow upgrade the phone to "Marshmallow" then you can try the instructions below. However, since manufacturers sometimes limit the devices ability to make this change, "Marshmallow" or not, there are no guarantees.
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.