If you have a green REFRESH button showing on the listing, there is a button nearby for entering new or revised information.
Welcome to Trulia!
I apologize for not finding and answering your question much sooner. In the future when you have a question about Trulia, please post it in our Using Trulia category so we can find it right away. It looks like you received a great answer from Paul however.
He is correct that only listings manually submitted via Single Listing Submit can be edited at this time.
We receive your listing information from JennyPruitt.com so you'll need to contact them to update any out-dated information on our site. Please ensure that they show the correct information on their site and within the data feed they send to us. Once they send us the new information, our display should update automatically to reflect any updates.
Please let us know if you have any other questions.