You have to completely dismantle the lower section of the laptop. You need to be careful of static discharge. (No fuzzy pink rabbit slippers).. Work on a Kitchen table, Hard surface floors. And if you can you should wear a static strap.. (Discharghes minute ammts of static to ground, Even static you cant see can render your RAM and other sensitive components inop) A grounded soldering iron is also advisable, (isolates the possibility of discharge here as well) Motherboard has to be removed and the connector needs resoldered. Scrape any carbon deposits carefully from the blades on the connector prior to resolder.. I generally pull them completely and check and clean. Good luck!
Ken LaDere
www.ikenfixit.com