The FS2012 operates as a slave device so if you set the Arduino up as a master device you can read from the slave. Start by taking a look at the examples for the Wire library in the IDE
From the datasheet it seems that the sensor simply sends 2 bytes on the I2C bus, so you should be able to read them. The first byte is the Most Significant Byte (MSB) of the value and the second byte is the Least Significant Byte (LSB) of the value. These can be combined into a single value with some manipulation
O i understand your sketch whitch connects to fs2012 and it looks its works (blinking led on sensor)
but how to read from it . How to read those 2 bytes and get some digits
The FS2012 is programmed to continuously output data to the I2C bus. (instruction from manual)