Read Value from Sensor using SPI

I bought a gas sensor.
But I don`t know how to read value using SPI.
I just want to read GAS value.
can you teach me how to read it?
I am sorry that I am not fluent in English.

WISE Gas Sensor(TED) Datasheet.pdf (548 KB)

readgassensor.ino (1.19 KB)

From page two of the datasheet:

Output: I2C Digital Output