How to play multiplayer minecraft through LAN, when both computers have the same IP Address?

How to play multiplayer minecraft through LAN, when both computers have the same IP Address?

Added (1). My two sisters want to set up minecraft so they can both play multiplayer together, through LAN.
We have tried to open a game to LAN on one computer, then have the other try to use direct connect method, but the second computer/minecraft doesn't connect. When they try to scan for a game on our local network, nothing comes up either.
They both have separate minecraft accounts but are both using the same IP address.
Are we doing anything wrong?

They won't have the same ip address at least not on lan. You just direct enter the lan servers ip address.