Jill Fickling-Conyers provided this tutorial on using digital brushes:

Brushes
1. Download a brush from a digital retailer or from any of the numerous sites available online (links below).
2. Save (the saved brushes should have an .abr extension) and unzip. My Mac automatically unzips but I've used WinZip (available online as a free download).
3. After unzipping, open photoshop (I'm using PSE6).
4. Select your brush tool from the vertical tool bar on the left (sixth tool from the bottom).
5. At the top of the photoshop window you should see "Brushes". Click on the small down arrow.
6. On the right of the drop down menu click on the small double arrow.
7. Click on Load Brushes.
8. Select the folder where you saved your unzipped brushes. Select the brushes to be loaded (select the brush with the .abr extension).
9. Your brush drop down menu should change to the brushes you just loaded.

You should be ready to start playing with the brushes! Remember to work in layers so you can correct mistakes and use a copy of the original photo.

The links:
I'll list some of my favorite sites for free and to be purchased brushes.
http://graphics-illustrations.com/category/free-downloads/page/3/ (on the Dec 12 entry see the Gratitude Word Art)
http://www.oscraps.com/shop/home.php?cat=287&treem=1

http://graphics-illustrations.com/downloads/ (if you sign up for the newsletter you have access to additional freebies)
http://www.designerdigitals.com/ddgallery/showgallery.php?cat=531 (freebie and to be purchased brushes)

I hope this is as easy to understand as I think it is. Brush examples in my Project Gratitude Album. Contact me if you have any questions :)