HAProxy Basic User Auth

[Hackzerhacker]

Hello,

i have a web server in a internal subnet wich i want to access from the outside via HAProxy with ssl offloading and a basic-auth. The server in my private subnet is not able to do the basic authentication so HAproxy should do the trick.
How can I do that? I already have the login mask but i don't know how i can proceed from here via the pfsense gui. There is simply no user/password list.
One thing I tried was to look for https://username:password@host.com/bla with a ACL but still no luck here.

What is the realm for?

Thanks