You both either have to be on the same wifi or connected via a vpn service like Hamachi. Then the host should share his/her IP. If you're on the same wifi, it's as simple as going into cmd and running 'ipconfig' and reading whatever number starts with '10.0.0.'
If you're using Hamachi(which is for if you two may not be close enough to use the same wifi, it's a downloadable application), then on the network you can just read the host's IP.
Then the host should start a multiplayer lobby, and if you don't seem to be able to connect it's worth trying to turn off the windows defender firewall temporarily as it sometimes blocks it.