I found this article on TweakHardware.com. It will walk you through adjusting the focus on that old computer monitor. It will also help you adjust the color and brightness of your monitor.
Many monitors display an unnecessarily bad picture quality. Several older monitors suffer from showing a very dark and blurry image. But it doesn't have to be this way! With a little knowledge and a couple of screwdrivers, we can make adjustments to achieve a sharper and/or brighter image.
The process is quite simple, but requires you to take the back cover off of your monitor. This is usually very simple and requires only a small screw driver. The guide on Tweak Hardware will walk you through the complete process.