Use the Gradient panel (Window > Gradient) to apply, create, and modify gradients. It’s helpful to show all options when working with this panel (choose Show Options from the panel menu).
The Gradient Fill box displays the current gradient colors and type. When you click this box, the selected object is filled with the gradient. By default, the panel includes a start and end color box, but you can add more color boxes by clicking anywhere along the color slider.