I had made a map a while ago with ArcGis Online. The map format was web map. I am trying to add a field to my layer, but there is no such option on the description table (Table options only provide me with 4 options, none of them is add field, I have tried both enabling/disabling editing).
It looks like your ports layer is a feature collection. In order to add a field to a table, you must use a hosted feature service: Show tables—ArcGIS Online Help | ArcGIS . To publish ports as a hosted feature service, hit save layer in the map viewer, and then navigate to the resulting layer item. A publish window will appear to give you the option to publish as a hosted feature service. (This requires an organization account).
Hmm, sounds like I either have to find that layer in some hard drive, or I have to make it from the scratch (since I do not have an organization account).
