1. Turn your Sony VGN-CS390JCP laptop over.
2. Find the laptop battery release button lock for your Sony VGN-CS390JCP laptop.
3. Now that your Sony VGN-CS390JCP 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-CS390JCP battery is removed, grab your replacement Sony VGN-CS390JCP battery for installation.
6. Insert the battery into the slot. Push the Sony VGN-CS390JCP battery towards the laptop and secure it in place.