Connect 2 wireless routers together on the same network

I need help connecting 2 routers together on the same network. The problem is that the house is a big house and I cant run a Ethernet cable outside to the guest house. I'm assuming I could get a 2nd wireless router (or 2 new wireless routers) so they can talk to each other. The computers in the guest house don't have wireless cards installed and need to be hard wired. Ideally, I could get an additional router and connect the machines in the guest house to it. Then, all the machines will be able to see and talk with each other (as opposed to running a cable). How can I set this up and which routers would you recommend that have a pretty long range?

Thanks in advance

Step 1: Make sure your old router is working.

Step 1a: Connect the Broadband modem to your OLD_ROUTER’s Internet (WAN) port. Then connect the computer to one of the four available ports on your router through an Ethernet cable.

Step 1b: Make sure that the Internet connection is working on your computer and on your wireless devices.

Step 2: Configure your new router

Most routers have an IP address of 192.168.1.1 so before you connect them, you need to ensure that they have been assigned two different IP addresses.

Step 2a: Shut down your OLD_ROUTER and the modem. Also unplug the Ethernet cable from the computer.

Step 2b. Plug the Ethernet cable into any of the numbered ports of NEW_ROUTER and connect the other end to your computer. Switch on the NEW_ROUTER.

Step 2c. Access the web dashboard of NEW_ROUTER (192.168.1.1) and change the local IP address to something like 192.168.2.1 so that there’s no conflict with the old router. Save the changes.

Step 2d. Test the SSID name of the new router and make sure it’s different from the old router. Also make sure that SSID broadcast is turned on. Save the changes.

Step 3: Connect the two routers

Step 3a. Connect the modem to the Internet Port of the OLD_ROUTER.

Step 3b. Connect one of the number ports of OLD_ROUTER to your computer.

Step 3c. Connect another free port on the OLD_ROUTER to the Internet Port of your NEW_ROUTER using an Ethernet or LAN cable.