Connect it the same way you would connect a shift register.
STCP->GPIO
SHCP->GPIO
DSIN->GPIO
DSOUT->DSIN of the next EasyPDLC in daisy chain or 'not connected'
OUT_EN->GPIO
VLOGIC->3.3V or 5V depending you your MCU logic votlage
VPOWER->5V
GND->GND
When you connect IV-22 VFDs refer to IV-22 datasheet, there is only two ways you can connect it, so it's not too hard. IV-22 segment names are written on the PCB.
While determining the orientation of IV-11, you can check where VFD pins 1, 2 and 11 goes. Pin 1 goes to 1V5 hole, pin 2 goes to GRID hole, pin 11 goes to GND. Please disregard the segment names written on the PCB; they are slightly mixed up.
For IV-6, note that the gap between the VFD pins(pin 12 is cut) on the VFD itself corresponds to the gap between the pads on the PCB. Please disregard the segment names written on the PCB; they are slightly mixed up.