this are adobe brush files.
1] Save this download somewhere on your pc.
2] Copy the file using Ctrl+C / Cmnd+C
and then go here:x:\Program Files\Adobe\Adobe Photoshop CS5\Presets\Brushes
[I hope you installed photoshop in your main partition]
3] Paste the copied file in this Brushes folder.
4] Open Photoshop, start a new file or an old one.
5] Select brush tool, get it inside image and right-click
6] You will see a brush properties box pop up, notice a small arrow on the top-right corner of this box. click it.
7] A box containing all preset brush sets will pop up.
8] Search your new abstract brush set in this box, select it. It will say, "replace basic brushes with this brush set?" click OK.
you are done! start using your new brush set.