First, you need to be using a phone that is running at least Android "Marshmallow" (or newer) or be able to upgrade to it. Second, you will need the instructions I am including below. And third, you need a phone that has not been restricted by the manufacturer from making this change. Which does happen.
NOTE: If any of the steps are missing on your phone, or they don't work for you, then you have a phone that either has an older Android version or has been restricted by the manufacturer.
How to turn the "External" SD card into "Internal" storage on "Marshmallow" a.k.a. 6.0.
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.
How to turn the "External" SD card into "Internal" storage on "Nougat" a.k.a. 7.0.
IMPORTANT NOTE: Be sure you start with a blank SD card. When the card is converted to "Internal" storage, it will be formatted (wiped) and encoded (making the cards data only readable by that device), so anything on it prior would be gone.
1. Go to "Settings", and then select "Storage & USB".
2. At the bottom of the list you should see the SD card's details, including the option to format it and make it "Internal" storage.
3. Once this is done, reboot the device and you can start running things from the card.
If you don't reboot the phone, some things may not work correctly, so make sure you do the reboot.
I own the LG Rebel 2 and the solution that was given to me did not work as all the other apps I tried to go from app to SD card I am totally frustrated and I think the whole process is full of s*** if someone has a correct answer please send it back to me I've tried everything and my operating system is 6.0.1 which qualifies me according to the explanations 6.0 is one of the latest 7.0 is the latest therefore I need a correct answer and not something that won't work I'm getting very frustrated like I said the whole process is full of s*** so someone has a correct answer please send it back to me thank you
Actually, that is the correct answer. If, as it says in the info, your device can't do this, is missing any of the needed aspects in the steps, etc., then the manufacturer has restricted this option on your device. Happens a lot actually. The only way around it is to root the device, which I would not recommend. If it is under warranty, that will void the warranty, plus you risk problems and even bricking the device. The most you would be able to do then would be to move files to the SD card, but not apps.