How to connect two monitors to one computer
You will need a computer with an open port, a second monitor and a vga or DVI cord (optional) and a GPU or pci video card, and a DVI to vga adapter.
look at the back of your computer and locate an available vga or DVI port.
The vga or DVI cord from the second monitor will fit the port. Purchase and install an AGP or pci video card if your computer does not have an available port.
plug in the second monitor and turn it on, connect the best monitor to the DVI port to optimize your hardware, restart your computer. If neither monitor comes with a DVI port use a DVI to vga adapter to connect the monitor. Setup the second monitor on a pc by right-clicking the desktop and then clicking properties. On the display properties window click the Settings tab.
click the display drop-down list and select external monitor, check the box extend my windows desktop onto this monitor and then click identify.
match the physical arrangement of the monitors by dragging the monitor icon then click OK.
arrange the displays on a mac by clicking system preferences and then selecting the displays panel, click arrangement and drag the icons to match the arrangement of your monitors.