How to open/publish files as hosted layers?

[HollyParker]

I have an ArcGIS desktop basic account and am learning how to use StoryMap. 

I uploaded a zipped folder as a KML Collection. As far as I can tell the data file is uploaded but not the feature layer, which is why I can't open it in the online map viewer.  To use any of those files to make an online map do I have to download it and then re-upload it through the add data button in the map viewer?

[OwenGeo]

Hi Holly -- Welcome to the world of StoryMaps! To get your data published I think you'll want to go to your Content page, then click Add item >> From my computer. That will let you upload your file and turn it into a feature service, if possible.

Follow up questions would be best to address to the ArcGIS Online‌ space.

[HollyParker]

Thank you Owen. What you suggested is what we did. You said "...and turn it into a feature service IF POSSIBLE"  - under what circumstances is it NOT possible? ArcGIS Online