Give a bit more details. Why do you think your graphics card is not working? Check the device manager to see if the graphics card is being detected. Did you perform a driver install/ uninstall recently?
Assuming it is a driver problem and you have an intel cpu and AMD gpu, check in the control panel in AMD's options whether switchable graphics is enabled.
If it is, and still you think the switchable graphics is not working, first download the latest display drivers from both intel's site and AMD's site. Then uninstall all display driver (both intel and AMD). Then install the intel display driver first and then the AMD driver. See if it works.