Extending Core JS; add modal on file upload success

Running NC 14. Preparing to share with users that need a bit of hand-holding and I’m trying to add a modal on successful upload. I’ve found this link: https://docs.nextcloud.com/server/14/developer_manual/app/js.html in dev manual, but it doesn’t indicate where to insert the example code to get the desired menu addition. Maybe I’m just dense; anyone able to point me in the right direction or offer a more detailed explanation? Thanks.

Thanks for moving this kind stranger/mod; I definitely could have used tags better. If anyone is interested in helping, I’ve got a bit more detail in my SO call for help.

running on a similar issue. How did you manage to use the file upload hook?