1. Turn your Sony VPCF121FX/H laptop over.
2. Find the laptop battery release button lock for your Sony VPCF121FX/H laptop.
3. Now that your Sony VPCF121FX/H 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 VPCF121FX/H battery is removed, grab your replacement Sony VPCF121FX/H battery for installation.
6. Insert the battery into the slot. Push the Sony VPCF121FX/H battery towards the laptop and secure it in place.