What is the Distinction Between Knowledge of The Path and the Fruit? It is said that this happens in close proximity. So it is always referenced together. What happens when you get the knowledge and how do to transition to the Fruit? What happens just before the knowledge of the path?
Knowledge of the path is simply the first realization of Nibbana as one of the particular kinds of Aryas. In other words, the first time a person experiences Nibbana as a Sotapanna, Sakadagamin, Anagamin, or an Arahat is called knowledge of the path. During the path-knowlege, the fetters are destroyed or greatly weakened . Knowledge of the fruit is the same except that it doesn't cut away at the fetters in the same way so it is classified differently.

Knowledge of the fruit occurs automatically after knowledge of the path. You don't have to do anything specifically to make it happen.

Here is a description of these knowledges from the Visuddhimagga:


  Here is a simile for this. An archer, it seems, had a target 3  set up at a distance of eight usabhas (about 100 yards), and wrapping
  his face in a cloth and arming himself with an arrow, he stood on a
  wheel contrivance (a revolving platform). Another man turned the wheel
  contrivance, and when the target was opposite the archer, he gave him
  a sign with a stick. Without pausing after the sign the archer shot
  the arrow and hit the target.
  Herein, change-of-lineage knowledge is like the sign with the stick. Path knowledge is like the archer. Path knowledge’s [675]
  making Nibbána its object without pausing after the sign given by
  change-of-lineage, and its piercing and exploding  the  mass  of 
  greed,  hate  and  delusion  never  pierced  and  exploded before, is
  like the archer’s hitting the target without pausing after the sign.
  
  And not only does it cause the piercing of this mass of greed, etc., but it also dries up the ocean of suffering of the round in the
  beginningless round of rebirths. It closes all doors to the states of
  loss. It provides actual experience of the seven noble treasures. 4 
  It abandons the eightfold wrong path. It allays all enmity and fear. 5
  It leads to the state of the Fully Enlightened One’s breast-born son
  (see S II 221). And it leads to the acquisition of many hundred other
  blessings. So it is the knowledge associated with the path of
  stream-entry, the provider of many hundred blessings, that is called
  knowledge of the path of stream-entry. The first kind of knowledge is
  ended.
  
  Immediately next to that knowledge, however, there arise either two or three fruition consciousnesses, which are its result. For it is
  owing to this very fact that supramundane  profitable  [consciousness]
  results  immediately  that  it  is  said, “And which he called the
  concentration with immediate result” (Sn 226), and “Sluggishly  he 
  reaches  what  has  immediate  result  for  the  destruction  of  the
  cankers” (A II 149), and so on.


(Visuddhimagga Chapter XXII 12-15, http://www.accesstoinsight.org/lib/authors/nanamoli/PathofPurification2011.pdf )