Garage Module v2.0.3 has adopted the new IPB Portal plugins system in IPB 2.1.x, so these instructions will be very short :)
PLEASE NOTE: These instructions are only for Garage Module v2.0.3 with IPB 2.1.x!
Quite simply put, all you need to do is add the appropriate tags to your portal. To see a list of available tags head into your ACP -> Tools & Settings -> Manage Portal Plug-ins.
Click the menu button next to the "Fusion Scripts Garage Module" line and choose "View Exportable tags". This will pop up a new window with the list of available tags you can add to your portal, such as " <!--::garage_featured_vehicle::--> ".
To show any of these content boxes on your portal head into your ACP -> Look & Feel. Choose 'Edit Template HTML' on your custom skin (not the imported Garage Module skin set). Click 'IPB Portal' on the left, and then click 'csite_skeleton_template' on the right.
Paste any or all of the exportable tags where ever you want.
Save, and you are done!