To change the brush size:

1. Choose the Brush Tool from the toolbar.
2. Click on the Set Brush Size dropdown menu in the toolbar at the top of your screen.
3. Use the slider bar to adjust the size of the brush you would like.

You can also highlight the number itself and type in a new value, or use the [ or ] (brackets) keys to adjust brush size.

To change the brush shape:

1. Choose the Brush Tool from the toolbar.
2. Click on the Show Selected Brush Presets dropdown menu in the toolbar at the top of your screen.
3. Select the shape of brush you would like to use and double click on it.