Q: can i install a graphic card in my macbook

It can't be done the graphics card is soldered to the motherboard.

not possible.  If you want a better graphics card, you'll need to purchase a newer computer.

Keep in mind that this is pretty much an industry standard with respect to laptop computers.  There are a few exceptions, but, for the most part, graphics processors and CPUs are soldered directly to the logic board (or "motherboard" if we're talking anything but a Mac).