Open the Brushes panel under Windows, click on the icon for the Brush Libraries menu at the bottom left and then on Other Library... Copy the sample brush files (AI format) into the Brush Libraries folder that opens and click on Cancel.After copying, the brushes are available in the Brushes panelunder the Brush Libraries icon.

Using brushes in Adobe Illustrator for free-form drawings and as an outline

To draw freeform shapes, select the brush and a desired brush tip. To apply the brush tips as contours, select a graphic object and apply the desired brush effect in the Contour panel by clicking on it. You can use the Strength parameter to set the strength of the brush effects.