Get him used to wearing his collar first of all, after a few days walk him around the house for 10-15 minutes at a time. Don't use the leash for a day or two, then when you want him to walk outside take the leash in your hand and go to the door and call him to you, put on the leash and take him out for about 10 mins. Gradually increase the time you are out with him and while doing so teach him how to walk by your heel, later you can teach him how to cope with traffic etc.
