I've used dual monitors for years: How I finally fixed the 'invisible wall' ...
My multi-monitor situation causes even MS's 3d screensavers to take some time exiting (5 or so seconds). I just tried 3d FlowerBox in software mode, and its default settings cranked my resolution way ...
Start by checking if your device and GPU support multiple displays. If its capable, ensure you have all the cables to connect the monitors. Next, hook up all the cables to the monitors and your PC ...