You need to get a copy of the datasheet
SRCK clocks the 8 bits into the Input Register one by one.
RCK then clocks all 8 bits together into the Output Register to drive the LED segments.
G/ can be tied low.
SRCLR/ can be tied high (Vcc) if you do not want to clear all the input registers at once.
SER IN is the data to be shifted in
SER OUT is the data to be shifted into the next device in line.