1. Turn your Toshiba L645D-S4040 laptop over.
2. Find the laptop battery release button lock for your Toshiba L645D-S4040 laptop.
3. Now that your Toshiba L645D-S4040 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 L645D-S4040 battery is removed, grab your replacement Toshiba L645D-S4040 battery for installation.
6. Insert the battery into the slot. Push the Toshiba L645D-S4040 battery towards the laptop and secure it in place.