1. Turn your Sony VGN-CS390JBB laptop over.
2. Find the laptop battery release button lock for your Sony VGN-CS390JBB laptop.
3. Now that your Sony VGN-CS390JBB 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-CS390JBB battery is removed, grab your replacement Sony VGN-CS390JBB battery for installation.
6. Insert the battery into the slot. Push the Sony VGN-CS390JBB battery towards the laptop and secure it in place.