To add brushes, gradients, plug-ins, and scripts to your Mac OS X follow the path as described below. Go to Users/homefolder/library/applicationsupport/GIMP.
Open the GIMP folder and find the appropriate folder…drop them into the correct folder.
Click image to enlarge.
Windows 7 & Vista users can watch a YouTube video on installing GIMP scripts here. (Note: Plugins - [*.exe and *.py files] are saved the same exact way, except they go in the "plug-ins" folder)
XP Users (especially those using Internet Explorer as a browser) click here.
Linux users read here. Also a few Ubuntu screenshots of GIMP Edit/Preferences/Folders (the correct folders for plug-ins and scripts are shown here):
At one point, I found myself on the GIMP Registry not knowing a thing about how to install scripts or plug-ins. The fundamentals of how this is done is documented on the GIMP.org site, located here. But before you go running off to check out that link for the information you desperately crave, stick around and view the screenshot instructions I'm posting below:
So you're browsing the GIMP Registry and you find a script or plug-in that sounds interesting and you want to try it. No problem.
If it's a .scm file, right click the actual link and choose "Save Link As". You'll see this prompt below:
Now you'll need to browse in explorer to save it to the right place. Since it's a *.scm file it needs to go in GIMP's script folder, as shown below (Vista):
In Windows Vista, the path to the GIMP scripts folder is C:\Users\Your User Name\.gimp-2.6\scripts. In Windows XP, the path is C:\Documents & Settings\Your User Name\.gimp-2.6\scripts.
The path for plug-ins are at the same location but instead of the scripts folder, you put the plug-ins in the "plug-ins" folder.
Notice that the plug-ins folder is directly above the scripts folder.
Plugins or scripts that come in a zipped file have to be handled differently, because you want to extract the files from the zipped file into the appropriate folders as shown above. Simply double-click the zipped file to extract them.
For adding new scripts, all that is required is that you refresh the scripts under Filters - Script-Fu - Refresh scripts. Adding new plug-ins, however, require that GIMP be closed and restarted. For most plug-ins, the most obvious place to find them is in the Filters menu, unless the Plug-in author instructs otherwise.
Scripts on the other hand are a little more tricky to find if the information on the GIMP Registry is lacking. One trick to finding where scripts are listed in the menus, is to open it and check out the register, located toward the bottom of the script file:
Sure enough, this script can be found under Filters - Light and Shadow, as indicated on the last line above.
Python plug-ins can be opened with an editor, but DO NOT OPEN executable plug-ins with an editor (e.g. someplugin.exe). If you cannot find a plug-in location in the menus, go to the Plug-in Browser under Help on your GIMP menu bar. (Thanks Saul!)
Most importantly, READ THE POSTS AND COMMENTS for the script or plug-in you are planning to use BEFORE you download it, and make a note of special instructions for the handling of that particular script or plug-in. Print it out, if you have to.
If all else fails, direct your comments to the author of the plug-in/script for logging errors and asking for additional instructions. The best way to get help is to clearly define your problem, including any error messages, and be specific about the problem. Don't post new comments on a new forum subject that read like this : "It's not working! HELP HELP HELP!" That fails to explain anything to anyone, and it's downright lazy and rude. Instead, run a checklist in your comments, that explain, that you downloaded the file correctly, it's in the right folder as indicated in the instructions. Specify your operating system and version of Gimp (i.e., using Vista 32 bit, GIMP 2.6.7) List error messages verbatim, and if it has a number assigned to it, include it.
We were all noobs at one point or another, so it's understandable that people are going to need a little extra help in getting started. The best thing you can do to help others help you, is be as helpful as you can, yourself.
If you use Notepad to save *.scm files, pay close attention to what you are saving it as, and where you are saving it to:
See the "Save as type:" showing Text Documents (*.txt)? That needs to be changed to "All Types"