Notepad++ - Associate file extension to a language's syntax highlighting

In Notepad++, you can associate a file extension to a specific language's syntax highlighting.

Do the followings:

1. Run Notepad++ as administrator. Otherwise, the settings will not be saved.
2. Navigate to Settings > Style Configurator.
   
3. Choose the language on the left side that you want your own extensions to match.
4. In the User ext. input field near the bottom, type in your file extensions without the dot in front of it. Multiple extensions are separated by a space.
5. For my case, I want files with .config and .fig extensions to style like XML.