Hopefully you can find your way to the Golf Course -- it's not far from the Ritz Carlton Hotel and new developments in West Bay area. From there, it's easy.

The Golf Course is on your right (Qatar University is ahead of you, a bit to the left), and as you're approaching the roundabout just past its entrance, you will turn right. Looks like it's a road to nowhere. You continue straight on this road for quite awhile, and then you'll see signs for Losail Track. Hard to miss...