As you can see in this screenshot, provided by user Hannah Anderson (and shared by social media consultant Matt Navarra), Instagram Creator Studio looks to be a secondary tab within Facebook Creator Studio - you can see the Facebook/Instagram toggle in the top middle of screen.
Not everyone has access to this option as yet. It's not clear exactly where it's being made available, but some will see it appearing in their own Facebook Creator Studio app, if they also have an Instagram account connected.
Within Instagram Creator Studio, users will be able to access a range of analytics metrics, including engagement stats, listings of when your audience is active, and demographic info.
It's worth noting that all of these insights are already available within your Instagram business profile tools, so it's not functionally adding anything new. But it would make these more easily available via desktop, while also giving you access to a combined asset library to be used across both your Facebook and Instagram accounts.
As noted, the new Instagram dashboard appears to be in test mode at the moment, and therefore is not available to everyone. But it's a helpful tool, and no doubt you can expect to see it rolled out to all some time soon - we'll update you as we get more info.