Sunflowers are one of the easiest plants to grow. You can try planting some of the seeds you buy at the grocery store if they are still in the shell, and they might grow.
However, there's a good chance that they won't become the big sunflowers you sometimes see or make many more seeds. You need special seeds that have been saved just for planting.
When you are ready to plant them, get the spot ready by digging it up and taking out all the rocks and weeds.
Poke holes in the dirt with your fingers and drop a single seed in each hole. Cover the seeds and give them a good drink of water with a garden hose or a watering can, and then wait about two weeks until you see the first green sprouts pop up.
Keep watering them during that time if the soil gets dry or it doesn't rain much, since they need lots of water to start growing.