The first thing you do is to dry the seeds. An easy way is to hang the flower in a dry ventilated area. Once the seeds are dry then you need to separate the seeds and soak in water over night. If you like salty sunflower seeds put salt in the water. My book says to make the water very salty. But then I work outside all day and lose a lot of salt.
Your final step is to roast the seeds. Take the seeds out of the water and place on a baking sheet and put in the oven at 200 degrees for 3 hours or until crispy.