Adding shapefiles to ArcGIS Viewer for Flex

Hello,
I am very new at the web GIS stuff. I must be missing something very simple and basic in terms of uploading my own data. I am just trying to set a up a viewer so that others can view some shapefiles that I have via an online interactive map. I downloaded the ArcGIS Viewer for Flex 3.1 along with the App Builder 3.1. I went through the on-line video tutorials and loads of documentation. Correct me if I am wrong but it is not possible to upload shapefiles directly into the viewer. Instead I need to save them as an ArcGIS Online map service?? I also read something about zipping them 1st. When do I do that if I am saving them to ArcGIS Online via ArcMap? From what I understand, if using the viewer itself then I need to to add the path for the service to my config.xml to access these data? If using the app builder then I have the option of adding them through "operational layers - ArcGIS Online - My Content". Am I on the right track? If so I am not sure why I am able to save my shapefiles to ArcGIS Online - My Data via ArcMap but my Flex Viewer doesn't recognize these data when I go to operational layers - ArcGIS Online - My Content. I can even see it in my ArcGIS Online - My Content website. Any ideas? Is there a simple way to add some shapefiles?

Any info is much appreciated!

Thanks
Joe