How to learn Bach Fugue in D Minor on piano?

Bach was a Music Genius.

Often the subject of replication and imitation, his musical pieces are unique and often hard to play. Take for example his infamous “fugues” piece, arguably one of his most detailed and complex pieces, how exactly does one play the difficult piano fugue in the key of d minor?

Here is Elena Kuschnerova performing Bach WTC-I Prelude and fugue in D minor BWV 851 at Elisabeth University of Music in Hiroshima on 11 May 2013.