I would recommend you to give your laptop to a near by computer store they will open the laptop for you.
If you want to do it yourself-
Remove all the screws you can see. Disk drive , ram vent etc.
Make sure to remove battery and disconnect adapter. There is space between upper plastic(covering mobo) and area below it. find it and use a thin screwdriver to open it. carefully clean it. the removing process is very dangerous that's why going to a store is recommended .