In order to post a property for lease on the Trulia site you must be registered as a landlord, property manager, or real estate agent. Currently, you are registered as a "Renter" so you will need to change your status.
Once you are properly registered then you can click on the "Rent" tab at the top of the screen. A drop down menu will appear with a tab that says "Free List a Property". Here you can post your rental listing for lease.
If you need any assistance you can contact a Trulia moderator at: 888-466-3501 M-F from 7am-4pm PST.
Hope this helps.
Prudential Connecticut Realty