1. Select the 14-pixel star brush (it's part of your default brushes) that looks like the one below:

2. At the top right corner of your screen you have three tabs: Brushes, Tool Presets, and Layer Comps. Click on the brushes tab and a menu will appear where you can customize the 14-pixel star brush you just selected.
3. Uncheck all of the boxes in the menu except for shape dynamics and scattering.
4. Click on the Brush Tip Shape option on the left of the menu and use these settings:

5. Now click on the Shape Dynamics option and use these settings:

6. Finally, click on the Scattering option and use these settings:

7. To save this brush, click on the little triangle on the Brushes tab at the top and select "New Brush Preset." Press OK and now you have a new sparkly brush! Here I used the brush around the text area of a graphic:

Experiment and have fun!