How to change the default look of popups on Attachment Viewer Instant App?

[ChrisDunlop]

Hello.  I'm replacing an old shortlist storymap with a new attachment viewer instant app.  In the new app, I have the "Feature label" function turned on so that when you hover over a point on the map, or over an attachment image, it displays the feature title on the image and a popup on the map.  The problem is, the popup formatting looks terrible.  Does anyone know how to change the popup formatting so that it resembles how it used to look in the storymap?  It doesn't have to be the identical, just a smaller size and getting rid of all the padding.   Thanks!