Copy the xml-files to "%APPDATA%\Notepad++\themes" and in a portable installation to "%Notepad++%\themes".
Or simply import it to Notepad++ by going to Menu -> Settings -> Import -> Import Style theme(s) option.
- Bespin.xml
- Black board.xml
- Choco.xml
- Deep Black.xml
- Dracula.xml
- Hello Kitty.xml
- HotFudgeSundae.xml
- Khaki.xml
- Mono Industrial.xml
- Monokai.xml
- MossyLawn.xml
- Navajo.xml
- Obsidian PyCs.xml
- Obsidian.xml
- Plastic Code Wrap.xml
- Ruby Blue.xml
- Solarized-light.xml
- Solarized.xml
- Twilight.xml
- Vibrant Ink.xml
- VS2015-Dark.xml
- Vim Dark Blue.xml
- Zenburn.xml