To draw an ellipse (oval), select the Ellipse tool and then click and drag anywhere on the artboard . If you hold down SHIFT as you click and drag, you constrain the ellipse to a perfect circle. If you hold down OPTION ( ALT ) as you click and drag, you define the circle from a center point.
As with other shapes , you can hold down the tilde key as you click and drag to generate multiple ellipses as you draw.
The other way to define an ellipse is to select the Ellipse tool and click anywhere on the artboard without clicking and dragging. The Ellipse dialog box appears, and you can enter an exact width and height.