To add a new brush, after either creating or downloading it, you need to save it in a format GIMP can use. The brush file needs to be placed in the GIMP's brush search path, so that GIMP is able to index and display it in the Brushes dialog. You can hit the Refresh button, which reindexes the brush directory. GIMP uses three file formats for brushes:

1.GBR
2.GIH
3.VBR

GBR

The .gbr ("gimp brush") format is used for ordinary and color brushes. You can convert many other types of images, including many brushes used by other programs, into GIMP brushes by opening them in GIMP and saving them with file names ending in .gbr. This brings up a dialog box in which you can set the default Spacing for the brush. A more description of the GBR file format can be found in the file gbr.txt in the devel-docs directory of the GIMP source distribution.

GIH

The .gih ("gimp image hose") format is used for animated brushes. These brushes are constructed from images containing multiple layers: each layer may contain multiple brush-shapes, arranged in a grid. When you save an image as a .gih file, a dialog comes up that allows you to describe the format of the brush. The GIH format is rather complicated: a complete description can be found in the file gih.txt in the devel-docs directory of the GIMP source distribution.

VBR


The .vbr format is used for parametric brushes, i. e., brushes created using the Brush Editor. There is really no other meaningful way of obtaining files in this format.

How to make it available?


To make a brush available, place it in one of the folders in GIMP's brush search path. By default, the brush search path includes two folders, the system brushes folder, which you should not use or alter, and the brushes folder inside your personal GIMP directory. You can add new folders to the brush search path using the Brush Folders page of the Preferences dialog.
Any GBR, GIH, or VBR file included in a folder in the brush search path will show up in the Brushes dialog the next time you GIMP, or as soon as you press the Refresh button in the Brushes dialog.

Info from gimp.org, Hope this helped (:  

You should link to the original page you got the tutorial from. link  

Posted by Dylan

You should link to the original page you got the tutorial from. link

fixed  

Let me rephrase that, Don't just post the text from their website; remove the text and just leave the link.  

Posted by Dylan

Let me rephrase that, Don't just post the text from their website; remove the text and just leave the link.

i find it conveniant on graalians  

Leave it as is. I don't go to a tread expecting to have to click a link that leads me to an alternate sight. Especially for the people with slow computers.

Good stuff