You cant. Sharingan isn't real. You can buy Sharingan contact lenses, but theyre very expensive. There is no other way.
Kakashi did not start out with the sharingan he got it from his friend in his childhood after his eye was cut in battle.
Well, Danzo can have sharingan by having absorbed uchiha shisui's color into his right side of the body. Obito did this to Kakashi when his eye was badly damaged. He put one sharingan eye into his damaged eye. Since Kakashi is not a member of the Uchiha clan, he cannot deactivate his sharingan eye. Because of this, he usually keeps it covered with his mask to conserve chakra.
sharingan
In the manga, Madara implanted Itachi's Mangekyo Sharingan into Sasuke's almost blind eyes. Therefore, the two Mangekyo Sharingan create Eternal Mangekyo Sharingan, restoring Sasuke's vision and preventing all future damage to his eye by using Eternal Mangekyo Sharingan. His Eternal Mangekyo Sharingan is yet to be seen.
Sharingan is not a jutsu. It is a kekkai genkkai or blood trait, like the byakugan. It a secret ablity only members of the Uchiha clan(sasuke and itachi's clan) has. The jutsus that can be performed using a sharingan are a kind of 'doujutsu' (eye techniques), along with byakugan and rinnegan techniques.
Tobi is not Madara Uchiha. He is Obito Uchiha, whose right eye is his original Mangekyo Sharingan eye. His other eye is the eternal one, considering he can evolve it to the Rinnegan form, it's most likely to be one of Madara's.
Tobi wields the Makengo Sharingan.
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You can't get Sharingan, it's just some made-up thing from Naruto. If it was real though, you would need to be the child of someone who has the Sharingan in their blood.
Eien no Mangekyō Sharingan, literally translated into English means Eternal Kaleidoscope Copy-Wheel Eye. This is the ultimate Sharingan. By taking the sharingan from a sibling (Mangekyō Sharingan or not) you can obtain this. It completely cancels out all drawbacks from the original Mangekyō including blindness caused by use.
No, it is not possible to have eye surgery to make your eye look like the Sharingan from the anime "Naruto." Eye surgery can correct vision problems or improve the appearance of the eyes, but altering them to resemble fictional characters is not a safe or feasible option.