- Locate the root directory of your Joomla! installation via FTP or any other method
- Download the latest language pack from http://sourceforge.net/projects/geshi/files/
- Unzip the file
- Open the folder where the extracted files are located
- Choose the language PHP file that you wish to install and copy it over to thelibraries/geshi/geshi directory
Image Credits: Photo by Isis França on Unsplash.