There are two ways to go about this.
First the best and costly way is to have a shop do it with the brake system flusher.
Second is the bitch caveman style way. Go out and buy 2 or 3 bottles of dot 3 brake fluid and a piece of 12" length of 1/8 inch rubber tubing (for the bleeder fittings) then grab a friend with strong legs and spend the whole day pumping, bleeding, pumping, bleeding etc.,etc. until the fluid that comes out the bleeder is as clear as the new stuff your pouring in the brake cylinder wells. Start with the rears and then do the fronts and be sure not to let the brake cylinder go dry because then you'll have to get all the air out :thumbdow