Obedience training in classes can start after six months old. Before then, you should train your dog in basic responsibility. Keep the training sessions short - the younger the dog the shorter his attention span. When its no longer fun, for you or for him, it's time to stop for the day. By the time he starts formal classes, your dog should at least have learned to come when called and walk calmly on a leash.
He should also have good manners in the house - obeying the limits you set. He should stand on command and permit someone to handle him. Not only is this good for the ring, your Vet will love it. We also usually teach the dog to sit. At ten weeks, he walks fairly well on a leash, comes happily when you call him and stands reasonably well. To make coming fun, get down to his level and call him in a happy excited voice. Praise him like crazy when he arrives. Although he should be working for your praise, an occasional treat (a cookie or liver flavored treat) will help the process of getting him to focus.
If you are interested in showing your dog in obedience, you will find it a worthwhile experience. Not many Bulldogs are shown in obedience, so they always attract attention. People always ask questions when we take our dogs out and are surprised to see they are so well mannered. It even helps in the conformation ring, where one of our Champions sat on his lounge outside the ring without moving while the other dogs are being shown. He made a great hit with those passing by.