Well, you'd find out what brand of card you have, go to the support section of the website for your card (i.e. ati.com or nvidia.com (not necessarily one of these, though)), download and install the newest driver for your specific model of card, and (probably) reboot. Then you ought to have a newer version of OpenGL, and Glest ought to run pretty well. I hope I was clear there...
!Dr.Dixie!