Niki from Trulia Customer Service here. Thank you for using Trulia to market your listings.
You can add open house information in the "My Listings" page. Log in to Trulia.com, hover your mouse pointer over your name in the top right corner of the page. The site navigation menu will appear as a drop down menu, click on "my listings". Your property will appear with an "edit property" button. You may click on the edit button and then choose open house or simply click on the blue text next to "Open House" under the pictures.
Please note that the open house information will go live to you listing page within 15 minutes, the open house can take up to 24 hours to fully process to the property details page on the site.
We are happy to help you with your listings or any other questions. Please feel free to contact us directly at email@example.com, or by phone 1-888-466-3501, Monday - Friday 7am to 4pm PST.