How to display subforum on custom page on phpbb forum?

How can I "extract" and display only posts from 1 subforum on a custom page of phpbb forum? I know how to make a custom page but what I would like to do is: Let's say I have this structure:

category1 forum1 --su开发者_如何学JAVAbforum1 --subforum2 category2 forum2 ...

I have made a custom page in which I would like to display only posts from subforum1? How can I do this? I am not a programmer so can you please advise me and I will try to do this on my own. Big thanks in advance!

This phpBB article explains how: https://blog.phpbb.com/2009/11/09/how-to-display-posts-and-topics-on-external-pages/