While that phone is running Android "Marshmallow" I believe it is one of the device that the manufacturer restricted that option on. That particular manufacturer does it with a lot of devices.
With that option missing, there is no way then to make the SD card "Internal" storage, rather than "External" storage, which is what would be need to run apps from it.
However you can still make room on the device. Just move all your photos, music, videos, etc, to the card and that would free up a lot of room.