Total Novice

I’m trying to follow This tutorial but being a total novice I’m not totally sure where to put the php.

I am using wordpress so have placed the xthml in the pages>html section. So where do I place the php and how do i call to it?

I would suggest to start with simple php files as in that tutorial, instead of WordPress and then when you have got understanding of fundamentals, you can start learning more complex systems.
To answer your question, php code goes into WordPress template files, not the page editor.

I see, so upload it side by side with the .php and .css files in my hosting control panel.
I’m about to start a php course but just starting on the javascript and I suppose trying to get my hand dirty in real life sites. Hope it works and thanks for your help