Click the Design tab. Click the Background Styles button,
and then click Format Background.
Click the Gradient fill option to display the available fill effects.
Click the Preset Colors button, and then select a color style.
Click the Type list arrow, and then click a type:
Linear, Radial, Rectangle, or Path.
Click the Direction list arrow,
select a direction, and then specify an angle.
Add or remove gradient stops, select a color,
and then drag the Stop position slider to specify a percentage.