On top of app is a bar on their right side is a "Device: XXX.XXX.XXX.XXX" and next is "Chanel: Side-Load a Channel" so click on a "Side-Load a Channel" link and select a "Import a Zip File" button and if your app is valid that's it.
To validate you can try just upload a package and run by regular way or try
npm eslintWell yea that is funny have no clue how to export, download or save it.
I share an idea about to write apps down as much as possible in BrightScript and avoid XML it's more dynamic and feel it has same performance as in XML.