Get to the Custom Brushes?

In the Options Bar, click on the brush thumbnail (it’s the second icon from the left) to open the Brush Picker, then click on the gear icon in the top-right corner of the Picker. In the bottom half of the pop-up menu that appears, you'll see all the different collections of custom brushes you can load. When you choose a set to load, a dialog pops up asking if you want to replace (delete) the current brushes and use these instead, or just add (Append) these new custom brushes to the end of the current default set of brushes. Here’s the good news: you can feel free to try out these brush sets because you’re always just one click away from re-loading the default brush set. In that same pop-up menu, you’ll see Reset Brushes. Choose that and it returns you to the default set of brushes.