Well, you've gotta start from the wheel furthest away from the brake master cylinder. Make sure your brake reservoir is full. Have a buddy pump the brake pedal 5 times and on the 5 pump he'll hold the pedal down. While he's doing that, you'll crack open the bleeder on the rear wheel furthest away from the brake master cylinder. The pedal will drop to the floor. You then close the bleeder and your buddy will release the pedal. Repeat that step until you get a smooth flow of brake fluid coming out of the caliper. Then move on to the third wheel furthest away from the brake master cylinder. Then the second and finally the closest wheel.
If the brake pedal hasn't firmed up by then, repeat the whole process and if it still doesn't firm up, you have a leak somewhere, probably inside the brake booster.