In this tutorial...I will show you how to use Brushes.
First, open up your brush. (If you already have brushes in your Custom Brushes that you'd like to use, don't bother opening up one.)
I am using this one:

Make the brush a Custom Brush. If you do not know how to do that, go HERE
Now open up the image you'd like to use your brush on.
I am using this one:

Now just go into your brushes, and place the brush on your image.
Mine looks like this:

So Obvioulsy this is pretty basic, but if you'd like to go into some more advanced tutorials on using brushes, you can go HERE