Here are very simple steps to update the DIRECT ADMIN skin to the Evolution Theme -
1. cd /usr/local/directadmin/data/skins
2. mkdir evolution
3. cd evolution
4. download the theme from http://demo.directadmin.com/download/evolution.tar.gz
5. tar -xvzf evolution.tar.gz
6. cd ..
7. Make sure you are at path /usr/local/directadmin/data/skins
8. mv enhanced enhancedORG
9. mv evolution enhanced
10. login to directadmin panel " https://IPaddress:2222 " and you should see the updated skin.