If you go to this page and click on the "Add brushes to Library" button, the library "Adobe x Keith Haring: Brush set" will open in a new browser tab. Click on the "Copy to Your work" button. Clicking that adds the public library of brushes to your library. When you open Photoshop, if your CC Libraries panel isn't open, go to Window > Libraries. You should see the library in that panel. To use a brush from that library, click on a brush to have Photoshop automatically select the Brush tool and load the brush for you.