|The simple way would be to connect the two routers and use the same subnet on both.|
If you click on my name above in my response you can read my "how-to" guide titled "Adding a Second Router" for details on how to do it. You'll want to use the single subnet scenario where you're connecting the two routers "LAN port to LAN port"
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.