Assembly of FlexRC Core with SirinFPV V2 Flight Controller is very similar to the previous version, which is described in How to assemble FlexRC Core DIY Kit
The main difference is that now ESC has built in 5V BEC and we are not required to use Pololu 5V, 1A Step-Down Voltage Regulator D24V10F5, but Pololu still offers more reliable results and you should consider to use it if you planing to fly on 4S+ batteries.
SirinFPV wiring diagram without Pololu
Wiring without Pololu but with ESC with built-in BEC is more simple and here is the wiring diagram for your reference:
SirinFPV wiring diagram with Pololu
Standard wiring diagram with Pololu: