How do I get HA virtualbox url?

I’ve recently installed with virtualbox and the instructions here: https://www.youtube.com/watch?v=vnie-PJ87Eg&t=559s
I’m not able to use http://<ipaddress>:8123/ and need somehelp

NOTE: pihole is installed with docker on the same machine

You need to know the ip address of the virtual machine (not the host).