Originally Posted by nathanj
1) Install Mega-Pack or single Themes from xmb.
2) Start multiMan, and go to "Filer Manager" by pressing [select+start]
3) Move pointer to [themes] tab and press X.
4) The list of Themes will show on the right pane, Hover over to it and click on a Theme.
5) Highlight and click om the .MMT file, done!!!
If you can't see all the themes, you have to press R2 to scroll down the list.
The Theme will automatically load and become the default, Enjoy.
And thanks Dean, for multiMan.