1. Turn your Apple MB990LL/A laptop over.
2. Find the laptop battery release button lock for your Apple MB990LL/A laptop.
3. Now that your Apple MB990LL/A 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 Apple MB990LL/A battery is removed, grab your replacement Apple MB990LL/A battery for installation.
6. Insert the battery into the slot. Push the Apple MB990LL/A battery towards the laptop and secure it in place.