Horses eat corn and wheat, and so do pigs, and cows and sheep eat corn and grass. Cows and sheep can always just graze on grass, which you have an unlimited amount of since its free and you don't have to plant it. But remember, cows will grow much faster than the other animals if fed properly. To plant, you press Mode, and keep on pressing until you see an empty field. Then you press Enter and you can choose what you want to plant.
Beans are the easiest to grow, wheat is second, and corn is the hardest.
When you go to feed your animals, the healthy food will be shone on the left side of the screen. Water increases the yield, and compost is a treat. Compost also increases the potential of your field. Every time you pick up your animals droppings, it adds to your compost. When you start your farm, you have 100 seeds.