After drawing your vector object, go to the “Fill” tab. There, set the “Fill With” to gradient (the second or third icon). A gradient bar will appear with 2 small squares under it. Press on the squares to chose the gradient color. If you want more than 2 colors on the gradient, just press the the color bar and a new square will be added at the position you pressed. These squares set the gradient colors. To remove a color (square), right click on top of it with the mouse and select remove.

On you object on the page, you will be able to move control points to adjust the gradient.