Concept of showing 4 different number on 4 segment together
Well welcome to tips for noobs here are some tips for you.
Lets back to Schematic
From here we know that you need to control a-dp pin to turn on segment led, COM1-COM4 pin to control individual segment.
If you think about it you can only control single segment butt you can switch to other segment after you control 1 segment to another.
So the idea is to control one then quickly switch to other segment(Scanning)
To do scanning you have to turn on LEDA-LEDG then turn on COM1 delay then turn off COM1 change LEDA-LEDG to other number then turn on COM2 and so on.
Here is a photo showing scanning. So time to start trying.