Welcome to Trulia and thank you for your question. Only listings submitted to us manually have this entry field for virtual tours. Other listings that are submitted to us automatically should show virtual tours automatically as well if those tours are submitted to us by the provider.
If your provider does not submit virtual tours to us, you might want to inquire with them if they can do so and direct them to the link below to review our XML feed specifications.
In the meantime, as a work-around, you can submit this information to us automatically via our 'One at a time' listing submission method. If you do so, that information won't manually override that which we receive automatically from other sources, however our system should pick up your virtual tour link and display that along with that information. I realize that work-around isn't ideal and may be fairly complicated to understand, so please feel free to let us know if you have other questions.
I will also send a recommendation to our team that we add the virtual tour field to all listings to make this process much easier in the future.