If the keycap is loose but still attached to the laptop, it can often be fixed by pressing down on the keycap. If the keycap re-attaches, a snap while pressing the key down is heard.
The first step in fixing your laptop is to turn it off and disconnect it from the power source. Next, remove any peripherals you have connected to it like a mouse or a USB key. Then, use a flathead screwdriver to pry off the cover around your laptop.