Download brushes from the Internet to your desktop. Websites like DeviantArt.org and Celestial-Star.net offer huge databases of free brushes.
Unzip the downloaded brushes by going to your desktop and double clicking on the downloaded files. Extract the brushes to a location of your choice.
Open PaintShop Pro. Click "File" > "Import" > "Custom Brush". The Custom Brush window will open.
Click the "Open" button in the Custom Brush window. Select the brushes you would like to add, and once again click "Open."
Select the brushes you would like to add from the list that is now displayed in the Custom Brush window. Select multiple brushes by holding down the "Ctrl" key while simultaneously left-clicking. Click "OK" to complete the importation process.