A hatch is a geometric pattern that uses the line color to create a design to fill a shape.
To select a pattern, click on it and click on OK to apply to the selected shape.
Note, that the hatch color is determined by the line color. The hatch will be applied on top of your existing fill color using the selected line color. If your line color and fill color match, the hatch will not be visible.
Make sure you either set your Fill color to "No Fill" or set the Line Color to be different than the Fill color.