1. Turn your Toshiba M500-ST6421 laptop over.
2. Find the laptop battery release button lock for your Toshiba M500-ST6421 laptop.
3. Now that your Toshiba M500-ST6421 laptop battery is unlocked, find the battery release button down.
4. Holding the laptop battery release button, gently pull your battery away from the laptop.
5. Now that your Toshiba M500-ST6421 battery is removed, grab your replacement Toshiba M500-ST6421 battery for installation.
6. Insert the battery into the slot. Push the Toshiba M500-ST6421 battery towards the laptop and secure it in place.