How do you upgrade the video card for an HP laptop?

My video card is 256MB and I find the screen flickers a lot when a lot is going on in the online game WOW. Do I need to upgrade the video card to 512 Mb or more and how?|||What type and brand of video card is it? if it is an integrated chip i would recomend taking it in to get an upgrade as its really hard to fit your own laptop video card