Your laptop has to actually support those upgrades; most with onboard graphics don't. Plus, there is more to upgrading laptop graphics than simply plunking a chip into a socket... if your laptop wasn't designed with that chip in mind, you will likely have heat issues. Not to mention that the power requirements may be steeper.
Some laptops were designed to allow graphics cards upgrades; but those upgrades must be purchased from the laptop manufacturer as they are proprietary. Chances are, however, if your laptop did not include a discrete graphics module from the start... there is likely no chance of adding one.