hi,
From the point of view seen where you did install chameleon:
put the theme with his folder <ThemeName> inside the /Extra/Themes/
Result should become: /Extra/Themes/<ThemeName>
Copy com.apple.Boot.plist to your desktop ( this is for your safety ).
Open it with a plist editor ( install apple developer tools ), some other plist editor or a text editor.
put at the end in your com.apple.Boot.plist , but before </dict></plist>
<key>Theme</key>
<string>ThemeName</string>
Check it.
Copy and replace the file back to the original place using sudo in the terminal.
HTH
LA