Well, since your phone came with "Lollipop" it won't be able to make the SC card the internal storage. However, that said, if you can upgrade the phone to "Marshmallow" you 'might', and I emphasize 'might' be able to get it to work. It will depend on if the phone is capable. There is no way to tell though until after it has been upgraded to "Marshmallow".
If you can get get it upgraded, then you will need to start with a blank SD card. Why? Because anything on the card will be erased when it is formatted to "Internal" versus the standard "External". Also the card would only be able to be read by that device, so if you ever want to back up any of the data off of the card, you would have to do it by sending it to another device or cloud from the phone. No using the card in another device.
How to turn external SD card into internal storage on Marshmallow.
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.
The only other option you would have is to root the phone. Which is not something I could go over with you, and would void any warranty you may have on the device. For information on rooting please visit the "Rooting, Jailbreaking & Unlocking" Forum
http/www.tomsguide.com/forum/forum-117.html.