Don't worry about the IP address. The two computers will find each other on your LAN.
Just go to...
Start>Help and Support>"Ask for assistance">Invite a friend to connect to your computer with Remote assistance>Invite someone to help you>
It will lie and say you and the other person must be connected by an Instant Messenger program. Click the "Advanced" link at the bottom of the screen.
Go through the setup process and save the resulting file on your hard drive, make the password simple, like abc or something just as simple. Make the time duration long enough to go do something useful, like 99 hours.
Copy the resulting file "RAInvitation.msrcincident" to your other LAN connected computer and launch it there. Fill in the password and click to connect. The other computer will pop up a screen asking if you want to allow the other computer to connect, click yes. On the controlling computer, in the top left, it will have a button to "Take Control." After you click that, the remote computer will have a new permission question if you want to allow the other computer to take remote control, click yes. The controlling computer will show the desktop of the target computer and you have control as if you were sitting there. Use the built-in on-screen keyboard to type anything needed in the remote computer.