To change the battery on a Casio Calculator JW-8LA, first, turn off the calculator and remove any paper from the printer. Next, locate the battery cover on the back of the calculator and use a small screwdriver to gently open it. Replace the old battery with a new CR-2032 battery, ensuring the positive side is facing up, and then reattach the battery cover securely. Finally, turn the calculator back on to confirm it’s working.