The CPU is locked in the socket. Before you can remove the CPU, you'll have to unlock the socket. Use a flathead screwdriver and turn the socket screw to "Open" position.
Lift up the CPU by the edges. Be careful, there are a lot of fragile pins on the opposite side of the CPU. You should be able to install the CPU back into the socket without any force.
There is only one correct way to install the processor into the socket. Both CPU and socket are keyed. When you are installing the CPU, make sure to match pins on the processor with holes on the socket.
Before applying thermal grease on the CPU, clean the surface with alcohol.
After the CPU surface is cleaned, apply a small drop of thermal grease.
Spread thermal grease evenly and install the heat sink.
ATTENTION! If you forget to lock the CPU in the socket, the laptop will not boot. If you install the heat sink without applying thermal grease, the CPU will overheat.