For these themes to work you will need an extension called 'Stylish'.
How to install Stylish:
1) Click here to download extension file. It should give you a download and say can't install. This is what should happen. If it doesn't, Right click the link, Save as and save it anywhere.
2) Next open Google Chrome and in the URL box type in: "chrome://extensions" (without quotation marks)
3) Drag the file onto this screen.
4) Click on 'Add', and you should now have Stylish installed! You can now go ahead with installing the theme.