Did you want to make your SD card become your device's internal storage without rooting your device.?, because rooting may Void your device's warranty.
FOLLOW THESE SIMPLE STEPS
Step 1 : Download ADB Driver -Download
Step 2 : Download ADB and FASTBOOT - Download
Step 3 : Enable USB debugging on your device and connect it to your pc/laptop using USB data cable.
Step 4 : Install ADB Driver on your PC/laptop
Step 5 : Now extract the ADB and FASTBOOT.zip
Step 6 : Open extracted folder and hold Shift button on your keyboard and press right button of your mouse then choose open command window here option to open command prompt window.
Step 7 : Type adb shell sm set-force-adoptable-true on the opened command prompt window and press enter.
Step 8 : unplug your phone and go to settings>>storage and USB>>SD card and format it as internal from the options.ENJOY