There are a few ways to fill a shape with a pattern in Illustrator. One way is to use the Polygonal Lasso tool. To use the Polygonal Lasso tool, click on the shape you want to fill, and then hold down the left mouse button and drag the cursor around the shape. The Polygonal Lasso tool will create a line of polygons around the shape. You can also use the Polygonal Marquee tool to make a shaped area into a polygon by clicking on it, and then holding down the left mouse button and dragging the cursor around.
