How do I add levels to a game program?

[caitlindlc]

My game is called Eat the Hay. In the game, the user controls a cow that moves to bales of hay to "eat" it. (The bales actually just disappear when the cow is near enough). This is for a school project, but I have to make this game more difficult. I wanted to add two levels and make each level progressively harder. However, I have no idea how to even add levels and how to go about it. I've attached the game, but I really need help!