I would like my excel, which had lat/lot along with various other details about those places, to be in my featured layer. When I add the excel to the map it only shows the locations with none of the details. I see that it says 'no attachments" however I assume there is a way to add the additional information to a field list or something however I can't seem to find it.
How are you adding your excel spread sheet to AGOL? I just created a simple spreadsheet that has 4 fields: Latitude, Longitude, Name and Type. There are just two records, and I call it Locations.xls.
In AGOL on my contents page, I click Add Item/ From Your computer and in the dialog, I navigate to my excel file. As I scroll down the dialog, AGOL is 'smart' enough to know that this is a Coordinates file, since I named the coordinate fields as such:
Here are my two points and one of the popups associated with one:
I'm not sure why you pop up is for an attachment; my suggestion is start over with a clean slate and try it again.