Check this link
with instructions on how to enable RDP through the command line. You will also need to make exceptions in the firewall rules on the remote machine. The link describes how you need to do that too.
Normally you can use the name of the computer as the address. The Windows network stack is smart enough to work with that data.
But if this on a invitation based event, Just install AnyDesk on your system and the remote desktop. The person on the remote end needs to give you their AnyDesk code and you can log into that machine after the remote user approves. Or you can set it up in such a way that you log in remotely without a need to be approved by the remote user. Also a possibility. AnyDesk is about as hassle-free of an experience as you can get for remote access.