How can I order posts within a category?

In the recent Forum post https://premium.wpmudev.org/forums/topic/how-do-i-rearrange-the-order-of-my-listing-categories you say that "listings will be displayed in reverse chronological order [but] There are ways to change this in custom code by modifying the query used to retrieve the listings."

Please can you expand on this further? Where is this query? What can I do to re-order posts alphabetically by Title?

Thanks, Ivan