Someone needs someone's DNA, and then summons them with a living soul to spare etc. lol go to Naruto Wikia and it's way more specific. Just look up Edo Tensei XD
It basically summons the soul of the dead from what's called the Impure World (Hell) and uses a living sacrifice as a vessel for the soul. The vessel then takes on a layer of dirt and dust to reflect the soul inside.
Unfortunately it only works if:
A. You can get a genetic sample of the person
or
B. They haven't been sealed by the death god, in which case their soul is inaccessible.
Unless:
C.
You're Orochimaru and go to the Uzumaki temple to release the souls from the death god to be reanimated.