Argon is the 12nd free XenForo style designed by Brivium, that flat, light, modern and simple.
LIVE DEMO: http://brivium.com/demo/argon/
1. Upload the contents of the upload directory to the root of your XenForo installation.
2. Go into your XenForo Admin Control Panel, click on Styles, and then click on "Import a Style" in the left-hand navigation list.
3. Click on the upload file field, and then navigate to and select the style-argon.xml file.