How Itachi was able to use Shadow clone? In Episode 452 of Naruto Shippuden,

Itachi used his shadow clone which was in Academy and he was himself training in forest. Since he is already very young then how come he was able to use Shadow clone. According to the teacher of Academy he was so talented that they graduated him but still how we was able to use it.

According to Fugaku Uchiha (His father), he has never used Shadow clone and also as per wiki Jutsu section its only states that he used only Fire release Jutsu. 

Since his Father was the only one who teach him various Jutsu then how he learned Shadow Clone? Is it his Father who teach him or Itachi alone was able to learn by himself?
It was never confimed in the cannon of Naruto-verse. However it can be inferred that such a technique can be self taught.

Naruto did it.  

With a shinobi as good as Itachi, who mastered the art of Sharingan at the age of 8, and having joining Anbu at the age of 11 Itachi wiki, it shouldn't be hard to self-teach the B-ranked Shadow-clone jutsu. 

Shadow clone Jutsu not imposing any blood-line limits (kekkei genkei)- and  Itachi being a prodigy above all others-  he could have copied the jutsu with his activated sharingan.