I cannot get the file to work/open to a searched location
I don't understand what this means. Can you choose MyTrails from the maps menu in Basecamp? Also, do you understand that this isn't really a "map", it's just a collection of POI's and trails. In most areas, you will not see anything. It is intended to be enabled at the same time as another map on your GPS. When you do this, the POI's and trails will be overlaid of the other map. But there is no way to do this in Basecamp, because it will only display one map at a time.