Getting Windows User with Express on Local Network

im creating a WebApp on a local network with React and Express.

People should be logged in via their Windows User.

I have Access to everything i need.

The Express server is hosted on a virtual Server in the local Network. I have read that it is not possible to get the Windows User by default. You need to have either Windows IIS host your Server or use Windows IIS as Reverse Proxy (which we did in my case)

No my question: How do i now get access to the user informations (that are hopefully brought to me by the reverse proxy)

-- I Assume they are gonna be in my request object but i couldn't find them...

Is there anything special i need to do? (Maybe another setting on the reverse Proxy?)