Unzip/extract the brushes.
copy the extracted files.
Go to:
C: -> program files -> Gimp 2-0 -> Share -> Gimp -> 2.0 -> brushes
paste the the extracted files you copied.
open your gimp and TADAAAAAM!!!
if you don't see the brushes try refreshing the brushes box
if you have trouble to understand all that you might wanna check
THIS