A cool example of what your locations post type archive page could look like

archive-wpseo_locations.php

<?php
/**
 * Template for displaying a map on the locations post-type archive page.
 *
 * @package Twenty_Twelve
 * @subpackage Local SEO for WordPress Archive page template
 * @author Joost de Valk
 */

get_header(); 

if ( function_exists( 'yoast_breadcrumb' ) ) {
	yoast_breadcrumb('<p id="breadcrumbs">','</p>');
} 

?>

<div id="primary" class="site-content">
	<div id="content" role="main">
		<h1>Locations</h1>
		<br/>
		<?php
			$args = array(
				'id' => 'all',
				'width' => 960,
				'height' => 600
			);
			echo wpseo_local_show_map( $args );
		?>

	</div><!-- #content -->
</div><!-- #primary -->

<?php get_footer(); ?>

Note that the Local SEO plugin will output the links to the locations inside the map div, so that when the map isn't loaded, the locations can still be reached. This also makes sure Google will be able to find them.

Now, for the rest of us....

Where does this go? Is this a page? ...page templates? ...bunch of php that makes a little bit of sense as I gingerly read it? ...how do I implement... whatever-this-is?

The code above goes into a new PHP file called archive-wpseo_locations.php which goes in the root of your theme's folder. Further info here: http://kb.yoast.com/article/102-template-files-for-local-seo

I have a more detailed template here - https://gist.github.com/bhubbard/f54b531f87690b857c35

so, if i use flatsome, I only need to add the file archive-wpseo_locations.php to flatsome root directory (with above code)?, does it work on child ?