Which Directory file do I embed the CustomPress code in?!

I asked this question in another thread a few days ago and still haven’t received a response, and I’ve seen a lot of other people asking this question, so I’m making it it’s own thread in the hopes that someone on the dev team will be able to answer it: for those of us not using the included theme, what is the name and location of the file that the single Listing is using as a template? I need to add the necessary embed code for CustomPress or other custom fields to get them to display on the front end.

I’m building a site for a client and I’ve been holding off on building the directory because I can’t solve this problem, but I can’t delay any longer. Please answer soon!