Insert a row into the "navigator_publics" table with your specifics.
If you're unsure of how to do this, you can modify this query (specifically the ordernum, caption, description, image and room_id) and run it to get the result you desire.
Code:
INSERT INTO `navigator_publics` (`id`, `ordernum`, `bannertype`, `caption`, `description`, `image`, `image_type`, `room_id`, `category_id`, `category_parent_id`, `enabled`, `recommended`, `typeofdata`, `tag`) VALUES (NULL, '1', '1', 'title', 'description', 'http://link to room banner img', 'external', '1', '-1', '-1', '1', '0', '1', '');