The free Public Account does not support publishing hosted feature layers from sources like shapefiles, CSVs, etc. To be able to publish that hosted feature layer you would need either a full ArcGIS subscription account, or a Personal Use account.
The Public Account has significant differences in capabilities than the others, notably besides the inability to publish hosted feature layers is the ability to "privately share." Using the Public Account, items are either visible only to you, or are completely public. There are many other differences...
If you are evaluating ArcGIS Online, I'd suggest a trial account so you can see and experiment with the complete set of capabilities. There are a number of beginner tutorials to help you get started, here's the complete collection:
https://learn.arcgis.com/en/gallery/#?p=agol&e=beginner
I would recommend these for getting started:
https://learn.arcgis.com/en/paths/mapping-and-visualization/
https://learn.arcgis.com/en/paths/try-arcgis-online/
https://learn.arcgis.com/en/paths/essential-arcgis-online-skills/
