I was looking into this myself & I understand you use a splitter to connect to another monitor, looked on eBay & see they are only about 5/6 quid plus a cable.
I've used a splitter before about 15years ago, but screens were a lot smaller then. The max resolution using a VGA port is approx. 2000*1500. If you use a splitter the bandwith is divided between the two screens, so you will be unlikely to be able to power 2 1080p(1920*1080) screens from a single VGA port at full resolution.
It would probably work using the HDMI port. However splitters have gone out of fashion now as most decent modern desktops can power 3 screens now straight out of the box - 1 HDMI, 1 DVI, 1 VGA