Make sure the jars and rings are clean and sterile (just put them in the dishwasher an hour before you start). Make sure you have new, un-used lids, for a proper seal.
Fill your waterbath canner and place on the stove over medium-high heat to bring the water to a boil.
Fill a separate large pot of water and bring to a high simmer. Add the peaches to the hot water (in batches, if needefor about 2-3 minutes. (This will help loosen the skins, making them really easy to peel).
Remove peaches to a bowl and rinse with very cold water. Peel the peaches (The skin should come off really easily). Remove the pit, and cut them into large slices.
Fill your jars with peaches as you slice them. You can fill them pretty full, and gently tap the bottle on the counter top to help them settle in the jars.
Next, place a small pot of water on to boil. Once boiling, add your new lids and boil for about 5 minutes to loosen the seal.
Meanwhile, make a simple syrup to add to the peach jars. Mix 2 cups of sugar with 6 cups of very hot water. Stir well to dissolve the sugar. Pour some of the the simple syrup into each jar, leaving 1/2'' headspace at the top. Gently tap the jars to release any air bubbles. Fill with more syrup, if needed to cover the fruit, leaving 1/2'' space at the top of the jar.
Wipe the sides and rims of the jars with a clean rag. Place a hot lid securely on top of each of the jars. Secure with the rings.
Use jar lifters or tongs to gently place the jars in your hot waterbath. Add more water to the waterbath, if needed, to cover the tops of the jars. Cover with the lid and bring water back to a boil. Once boiling, process the jars for 25 minutes.
Place a large towel or dishrag on your countertop. After the 25 minutes is up, use tongs or jar lifters to move the jars onto the towel to rest.
After an hour or two you can check the seals to make sure they all sealed properly before you store them. When you press on the center of the lid it should be sealed down. If you hear or feel it pop back at all, then it didn't seal properly, and you need to refrigerate the bottle and eat it soon.
Allow the jars to cool completely before storing them in a dry place.