Erica from Trulia here. In order to brand a listing, you must first claim that listing as yours. You can do that in two ways.
1- You can go to your my listings page ( http://www.trulia.com/account/listings/ ), click search where it says "find your listings on trulia" on the right, check the check boxes for your properties, and your photo and information will now appear on the details pages for the properties that you've chosen to brand.
2- You can search for your listings on our home page, and on the details page for that listing you will see a link that says "Brand It!." Click that link and you will start the process for branding your listings. You will need to do this for each of your properties.
I hope this was helpful.