There are two slots on the stock, upper and lower. Leave the Triglide in place on the rear of the sling, and start by passing the webbing thought the lower slot, from the left side of the rifle to the right side (vice versa if you are left handed). Pass the end back through the top slot and then secure through the Triglide buckle. You've effectively created a loop of sling around the stock. You should adjust the rear Triglide as close as possible to the stock and if you can, double the webbing back through the buckle.
Best I can do with out a pic...