To add a business listing you must first be a registered user. Once you have registered and confirmed your registration via the automatic email response you receive from the site you can add business listings.
On the marketplace page you will see an 'add listing' item in the left most column beneath the heading 'directory categories' once you click on that you will be presented with a place to put in your listing. Your listing can use HTML and link to external images if you desire.
Please let us know if you have any difficulties with this and we'll sort it out.