How did Kakashi learn sharingan?
Kakashi gets his sharingan from Obito Uchiha. You can see it in
The Kakashi Chronicles part 2.
After Kakashi had his eye badly injured by a kunai a large
explosion traps rin, kakashi, and Obito in a cave. Obito pushes
kakashi out of the way before he is crushed by a rock, causing
Obito to get crushed. Slowly dieing obito gives kakashi one last
request. To take his sharingan and protect Rin.
Rin, being a medicle ninja, transplants Obito's sharingan eye to
kakashi's slashed eye. Obito did this because he could never admit
his love for Rin. He did not want her to die so he gave kakashi
immense power,via sharingan.
That is how and i hope i helped