We'll create fresh WordPress site with Embed OSM installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Embed OpenStreetMap on the page/post using [embed_osm] shortcode.
On the plugin setting page, you can specify home position, size of map, type of marker and so on.
You can specify map layer via shortcode and plugin setting page.
Map layer seleced by shortcode is higher priority than plugin setting.