Step 5 - Add A Gradient
Change your BACKGROUND color to "#7BCA03" and select your gradient tool. Up top make sure you selected the "Reflected Gradient", its' the 4th one from the  left. Now holding the "CTRL" key down on your keyboard click on the layer entitled "Sticker". Now starting in the top left drag a diagonal line like this and then let go. You should end up with a small gradient like this.