Facebook Graph API – Connect to Client Instagram

I’m a first time user for Graph API and it’s complicated as heck on the management side of things.

I want to connect my App to a separate instagram business account (My partners) so I can write her some metrics tracking she can use to analyse her follows and unfollows.

I’ve just realised I can’t just use the Facebook App Review process because they want public access to it to check it, but this isn’t a public application, it runs on a home server on a cron that checks once a day to update a metrics CSV.

How do I allow my Facebook account (developer) to access someone else’s Instagram business account? I feel like there must be a way to connect them but I can’t figure out how.

I’ve gotten as far as allowing Facebook Login, and accessing my personal facebook account with extremely limited data (literally just my name and a profile photo link). I can’t even figure out how to give myself access to my own feed!

I’ve read the docs, I don’t get it.

Many thanks.