One of the great things about Script-Fu is that you can share your script with all your GIMP friends. There are many scripts that come with GIMP by default, but there are also vast quantities of scripts that are available for download all around the Internet.
If you have downloaded a script, copy or move it to your scripts directory. It can be found in the Preferences: . →
Do a refresh by using
→ → from the toolbox. The script will now appear in one of your menus. If you don't find it, look for it under the root file menu filters. If it doesn't appear at all, something was wrong with the script (e.g. it contains syntax errors).