Once you have videos on your site, you should choose some to feature. The front page of your MiroCommunity site includes a featured, or "Editor's Picks" area on its top, so if you don't feature any videos, this area will be empty.
Administrators can feature videos from the Review Queue if they are just being added to the Miro Community Site, or through the Bulk Edit page if they were approved automatically or are already on the site.
In the default theme, the videos will scroll through the featured video area.