stephencottontail on "Need help creating child theme for Arcade Basic"

You can use the code I provided to properly enqueue your editor stylesheet:

function my_theme_add_editor_styles() {
    add_editor_style( 'editor-style.css' );
}
add_action( 'after_setup_theme', 'my_theme_add_editor_styles' );

That snippet of code should be added to the end of your child theme's functions.php, right after this snippet (from your original post):

<?php

add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );
function theme_enqueue_styles() {
wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' );
wp_enqueue_style( 'child-style', get_stylesheet_uri(), array( 'parent-style' ) );
}

The TinyMCE editor is the html editor on in the wordpress admin correct?

Yes.

And this is basically to add extra features to use in the there only, nothing to do with the front end of my website

Not really, no. All this does is change how the HTML editor looks. If you'd like to add features to the HTML editor, you should try a plugin instead: https://wordpress.org/plugins/tinymce-advanced/