Hello Al..
What are you trying to do Al? Knowing that, someone could provide specific advice.
MIT really does not provide a hand fed tutorial. For examples for your question you might start here. Read the examples; there are a few tutorials w.r.t. Markers. Also search the community forum for Maps, geojson, json, linestring, polygons etc. where you should find discussions about how to use specific Map components.
The National Parks tutorial) demonstrates how to plot multiple run time markers using a csv file to an OpenStreetMap. Use the list from csv Block to convert the csv to a List. What you do depends on how you make your List, where it is stored or is downloaded from.
Using Polygons Extract Json (Polygon.PointsFromString) Data in a txt file - #5 by SteveJG
FeatureCollection references in old Forum
There are examples in the haystack of topics shown above. Here is a way to create run time Markers from a List (converted csv)
. There are simpler ways to use the Block but one has to know where the information for the CreateMarker Block originates and how you intend to use the runtime marker. Often, it is simpler to just use one or two design time Markers.
Regards,
Steve