How to find my Minecraft server IP address?

My friend wants to join my world on Minecraft PC. I can't find out where it is. But I think it's something to do that my dad disabled multiplayer (I'm not actually sure if he did or not, but he does a lot, so making an assumption would be safe). This site I visited earlier today was a total troll. Me and my friend both tried it and we got the same thing. Please help soon. And by the way the trolling site was named whatsmyip.org, so don't try it.

Added (1). P.S.: I have a Windows 8 Asus laptop, so I can't necessarily search any programs on my desktop.

Kona

Whatsmyip.org isn't a troll site. Its actually a valid number that you need to input.

You need to give that external ip address at the top of the website to your friend in order for him to access your server.
If he can't login with that then that means you probably didn't port forward and/or your personal firewall is blocking him.

You must open tcp port 25565 in your firewall and from the router settings
Type 192.168.1.1 into your browser
Find where you need to go to port forward
Then forward that port from your private ip address

Matty