Maximum Number of Zones

[HereComesTheRain]

Hello Everyone.  

Was sidetracked and unable to make any headway with my irrigation project until now.

Chose to go the the DIY RELAY route as described at https://github.com/Dan-in-CA/SIP/wiki/Relay-interface 

I'm a NOOB at this stuff and could use a little more detail on how to construct the irrigation control.

Using (3) 8 Channel Relay Boards, Secondary Power Supply

For example do the jumpers go from the bread board to the 1-8 pins on the relay board?

What about the power? On the following page https://github.com/KanyonKris/relay_board/wiki a wall wart powers a 4 zone relay board/valves.

How would I configure to power (3) 8 Channel Relay Boards with 20 zones?

I'm a visual person so feel free to provide a sketch or photo.    

Hope everyone is well.