It is possible to make it one large network but i need to know more about your setup and your needs.
Do you need this to be one network with three separate IP subnets (192.168.1.x, 192.168.2.x, and 192.168.3.x) or all on one subnet?
If you want to keep a device on one network from being able to access a device on another one then you want separate subnets.
Do you need any devices to specifically not have internet access?
Do you want all of the wireless networks to use the same network ssid (the name of the network that you connect to) or seperate ones?
What are the model numbers of your routers?
You will need to dedicate one as your primary router. Your other two routers will need to be set as access points (bassically an...