Read these declassified accounts of the Trinity Test on the 59th anniversary of the first detonation of a nuclear device. I’d also recommend reading the Pulitzer Prize winning The Making of the Atomic Bomb by Richard Rhodes. Or you could watch Trinity and Beyond: The Atomic Bomb Movie, which is narrated by William Shatner and contains a lot of declassified film of Atomic Tests. Even more information, including many pictures and video are at nuclearweaponarchive.org.