Looping through child posts of a parent post

Using ACF, I created a custom post type (State Parks) and set it to be hierarchical.

I then created a single page template that is tied to the State Park post type with a conditional statement. The name of the single page template in Cornerstone is State Park Overview.

I created 3 additional posts (fees, dh hiking trail 1, dh hiking trail 2) with this custom post type and selected the post “Dead Horse Point” as the parent post in the child posts.

Single Page Template - The Looper Provider: Whether I use the query builder or query string in Cornerstone, I am unable to pull the 3 child posts of the parent post (Dead Horse Point).

I found this, but I don’t know where to place this code. To target children of the current post/page you are viewing, you can use a Dynamic Content string like {{dc:post:id}} as the value for the post_parent parameter.

Can you please tell me how to pull in the child posts of a current/parent post on my page template? Thank you.