Poppy seed is very fine, almost dust like, and needs light to germinate. The seed needs to be sown on the surface of the soil. It may help to mix the seed with a little fine sand and sprinkle this on the surface of the garden. I don’t bother doing that but just put a small pinch of seed on top of cleared soil every 30cm or so. In recent years I have had to turn the sprinklers on to the garden before sowing because autumn has been so dry. After sowing I gently watered the seed with a fine rosed watering can. After sowing the soil surface has to be kept moist until germination takes place which is generally within a couple of weeks.