Remove the plastic case by gently bending back towards the screen. You can bend the screen all the way back if that helps.

For the motherboard the optical drive will be removed already. However for the lower case it is not necessary that it be taken out.

If you are having trouble removing the upper plastic case (and LCD) from the lower case, there may still be a wire connected to the Wi-Fi adapter. Turn the laptop over, open the Wi-Fi module access panel and remove the + and - leads for the Wi-Fi antenna.