It is usually not possible to install a video card in a laptop as the graphics-processing function is integrated into the motherboard. It may be possible to attach the laptop to an external graphics enclosure that contains a GPU intended for desktops.
Though they are rare, there are some laptops that are designed with removable or optional graphics cards, such as the Lenovo Y510p.
If a laptop does not have a removable graphics card, however, another option to look into is an external graphics amplifier. Alienware manufactures one for its Alienware 13 and later models, and MSIs Gaming Dock Station connects to a wider range of laptops.