Okay, newb here. I do know you can’t add php in the html code section of a post via the admin. (without widgets etc)
Where is the mypagename.php file? How do I get to it?
If its via ftp, would you please specify the exact file path?
page.php is a default page template file. And you can find that file inside your active theme directory.
About the Instructions I am working on it. All instructions will be available with next release.