robert,
I'm not much of a runner either. when I was able to do 2 miles in 20 minutes, taht was a huge accomplishment. I have short legs and was a chubby, lazy kid for the first 20 years of my life. *sigh*
All you can really do, is go jogging. When you can't jog anymore, switch to a brisk walk for a couple minutes...then go back to a jogging pace. Keep cycling back and forth like that for 20-30 mins. If you can do this on a treadmill, perfect! Don't worry about jogging any faster than 6mph - that's a 10 minute mile pace.
Basically, its gonna come down to practice, and conditioning yourself to run further. Rise to the challenge!