Well it depends on a multitude of factors. First, I need to know what video card you got. Second the monitors both need to be connected to the video card via display outputs (DVI, HDMI, DisplayPort, etc.). Lastly it's a matter of if your video card supports it but all video cards nowadays should support dual monitors.
There are some factors involving software and drivers, but the physical part matters first.
Answer these three and I can help you further.