You've obviously got the MAX7219's working.
What you need a grasp of now is using arrays to send them data.
Here's the way I did it.
I have an array, called displayArray.
In this example it is 64 bytes, displayArray[0] to displayArray[63]. In my code, I made it 1022, so it can be stored in EEPROM & saved during a power outage.
There is a pointer that keeps track of where the data will start that will be sent to the MAX7219s, called displayStart.
You load up displayArray by whatever means (preload it in the pre-setup byte array definition for example).
Then you use the displayStart pointer and copy the data to the MAX7219.
So if displayStart = 7, then the data from displayArray[7] would be copied into display0 register1, up to displayArray[14] going into into display0 register8
next, display1 gets displayArray[15] to displayArray[22]
and so on for display2 and display3.
That data sits there for 100mS, then displayStart gets bumped to 8, and the process starts again.
(NOTE -the names below the diagram should have read display0, display1, display2, display3 - little copy & paste error)
