Alright, Press shift+F9, that will open the color window. under where it says "type" select solid for an ungradiented fill, select linear for a straight gradient, select radial for a circular gradient.
Next, do you see the little arrows pointing to places at the bottom of the window with the gradient?
double click an arrow to change it's color. Or drag it to change where on the fill the color will appear. Drag an arrow off the bar it is on to delte it and click a place on the bar to make another point in the gradient.
Hope I helped.