You need a post hole digger and cement. YOu have to measure out the area that you are putting the post. YOu can space them apart every 6-8 feet. You dig the hole and have the cement prepared and when the hole is done you put the cement around the post. The cement should come with directions for mix. You should put the post down at least 10" for it to stay in the ground well.
I don't think 10 inches will quite do it. A good rule of thumb is half the heaight of the fence but nothing less than 30 inches deep. The diameter of the hole should be at least 4 inches greater in diameter than the post but nothing smaller than 6 inches. Make sure your holes look more like a bell than an ice cream cone because frost in the winter time can actually lift the post out of the ground.