WordPress.org

1. Upload dtabs.php to your Wordpress Plugins directory.
2. Activate dTabs in the Plugins section of the admin control panel.

Please note that if your theme is not pre-enabled for dTabs you need to insert the dTabs template tag (dtablisttabs) of code into your theme before your tabs will appear on your blog, alternatively/in addition you could ask your theme's author to pre-enable your theme.