1. Turn your Sony VGN-TZ191NX laptop over.
2. Find the laptop battery release button lock for your Sony VGN-TZ191NX laptop.
3. Now that your Sony VGN-TZ191NX 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 Sony VGN-TZ191NX battery is removed, grab your replacement Sony VGN-TZ191NX battery for installation.
6. Insert the battery into the slot. Push the Sony VGN-TZ191NX battery towards the laptop and secure it in place.