Create simple WP post template

I need a simple WP blog post template for the Elegant Themes Deep Focus Theme (from 2018) which would display when an author selects category "Poetry" for a new post on the "add post" link. Instead of standard writing block, author would see 4 custom fields: Poem Title, Poem Text, Poem Author, Poem Date; when completed and post is published, content would display on front end, using the existing theme's css. I can supply a copy of the Deep Focus child theme, or just the [login to view URL] file as a starting point if that's all that's needed to make this template. Don't need anything fancy, just simple and usable for tech-challenged authors. Am attaching a screenshot of how the front end page should appear (poem content in left panel, sidebar is unaffected).