You would have one router and the others set up as repeaters (switches). The main router will have the internet at the WAN port and cables from the LAN ports that will go to the repeaters WAN ports (actually I was able to use a WiFi router as a WiFi switch using only one LAN port since the WAN and the other 3 LAN ports were fried by lightning, so you can use a LAN port too). This is the simple way. But if you live in an american (or similar build) house, I bet you need only 2 WiFi points installed in diagonaly opposite corners of the house.
Now here is something different. I had a project where I had to link 8 separate networks wirelesly. There were these restaurants scathered along a street in the centre of the city and cables could not be wired across the street. All of them had 2 computers, one for orders and one for video surveilance (4 cameras). All data was going to the server in the owner's office. So, we had a regular router providing the DHCP sevice to all network and that one was wired to a Asus router configured as a wireless bridge. Every small network had it's own Asus router configured as a bridge and these routers would only talk with their counterpart whose MAC address was in his list. So A would talk witn B, B would talk to A and C and so on, and somewhere in the middle was X tied to the DHCP router. Total distance from one end to the other was about half a kilometer and the comunication between the bridges was zig-zag-ing from one side of the street to the other, for better line of view. The wireless connection between these small networks was undetectable to the regular wireless clients and it would not communicate with anything with a MAC address that was not on the list. This is something overkill for you, but I just wanted to show you what can be done.