Jennifer,
according to this there is a drag and drop option within ArcGIS Online, I just tried it and it worked (with a lat/long cvs file).
Try it with the file I have attached.
Since the Webappbuilder runs off an AGOL map, there might be something you can do.
Wish I could be more help!
Tim
Tim -
I will definitely try this out!!
Thanks for you help!
Will let you know in a bit if I got something to work in a web app...
Nif