Start by first crafting a hoe. It can be made simply with 2 sticks and 2 wooden planks. Once you craft it go over to an area with grass beside a pool of water and till it by tapping on the blocks.
Once you have done that we need 3 seeds. You can get them by tapping on tall grass and they will randomly drop. When you get them go over to your tilled land and plant all 3 seeds.
Now you need the crops to grow. You can simply wait or you can turn some bones into bonemeal to speed them up. Either way wait until they can be harvested and get your wheat. Now simply craft your 3 wheat into bread and achievement unlocked!