Firstly, make an image. Now make a new layer. You can paint, place text or
make an image on this new layer. The image you've made will be the brush.
Second thing is to define the custom brush by going to Edit menu and click
the Define Brush caption. Next it will prompt you to enter your custom brush name.
Then select the paint brush tool from the toolbar. Now you should see our custom brush in
the pallete. Click on it to make it active.
Now you're ready to paint on the image using the custom brush you made.