Well first you will have to be running Android "Marshmallow". Second you will need to use the instructions below to change the card from "External" storage to "Internal" storage. Third you would need to have a device that 'allows' for making this change ("External/Internal"). Some manufacturers restrict this option.
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...