1. Turn your Sony VGN-FW139N laptop over.
2. Find the laptop battery release button lock for your Sony VGN-FW139N laptop.
3. Now that your Sony VGN-FW139N 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-FW139N battery is removed, grab your replacement Sony VGN-FW139N battery for installation.
6. Insert the battery into the slot. Push the Sony VGN-FW139N battery towards the laptop and secure it in place.