Twenty Nineteen Custom Template

I want to create a custom template for 2 pages on my site. I’ve copied and renamed page.php to mytemplate.php and uploaded the file into my child theme folder. Now when I go to create a new page, I don’t see this template. Twenty nineteen theme in the admin’s Add New (page) doesn’t even have a template dropdown menu.

What else should I do, in order to have this new template appear? Thanks