Place the downloaded background folder bearing the name of the file you downloaded into "C:\Program Files\Stardock\ObjectDock\Backgrounds" folder.

Then create a tabbed dock (or use one you already created) > right-click dock > Dock Settings > Tabs & Styles category > highlight a tab name in the list > use the "Style" drop-down list to select the new tab style > save theme.

Note - Tabbed dock backgrounds are listed at the top of the list.

For more information on working with the ObjectDock file structure, you can read my mini tutorial here http://corkyo.wincustomize.com/Articles.aspx?SID=5463&AID=82930