Loading specific post from php.

I’m almost done with my site (I think this will be my last question!)

Everything works, except for getting my homepage to load the correct post. I have a couple test posts saved under a category (and all of the posts are displayed in the navigation). I currently have “Test post” and “Test post 2”
When the page loads, the script I have loads “Test post.” However, I need it to load “Test post 2.”
I can’t reorder the posts, either. They need to be in a specific order.

Can anyone help me with this? I’m really new to php.

Here’s my site:
https://www.dougberkytheatre.com

Here’s my code:
https://wordpress.pastebin.ca/1040937