If all 3 of you are on the same wi-if network, all you need to do is add the host's IPv4 address using the 'add server' button at the bottom of the multiplayer window. You can usually find your IP address with a quick google search.
If you're not on the same network, you can use a program called LogMeIn Hamachi. One player needs to create a group name and login in Hamachi, while the other players join the group with those login details. Then, you can join the server by manually adding it using the 'add server' button as mentioned above.