How to add brushes?  

Do you want to know what should be done with the brushes that you have downloaded from other source. You have to just place it in your brush folder in the adobe photoshop instalations folder, which normally would be located at: C:\Programs\Adobe\Adobe Photoshopxxx\Presets\Brushes. After adding the ABR file to the location, just right click on your canvas as you normally do to choose a different brush. Then click the little arrow on the drop down menu and click "load brushes" as shown in figure 1 or choose the brush directly (should appear on the second drop down menu that apears after clicking the small arrow).