Looks like it uses SPI.
Wire it this way:
FLASH 1 SI <- Arduino MOSI (D11)
FLASH 2 SCK <- Arduino SCK (D13)
FLASH 3 RESET <- +3.3v
FLASH 4 CS <- Arduino data pin, typically D10
FLASH 5 WP <- Arduino 3.3v
FLASH 6 VCC <- Arduino 3.3v
FLASH 7 GND <-> Arduino GND
FLASH 8 SO -> Arduino MISO (D12)
Set the CS pin LOW to activate it.
Use SPI.transaction() to send commands and receive results.
Set the CS pin HIGH to end the command.
Flash