What was used to carry the atomic bombs?

Answer

The intent of your question is not clear. During World War 2, the bombs were carried to their targets in B-29 Superfortress bombers.

During the Cold War, several jet aircraft were capable of carrying nuclear bombs; some were large mega-ton size and some were small tactical size.

Nuclear bombs can be carried by Interconteniental Ballastic Missiles (ICBMs).

This Question was posted under Physics category, so maybe your question is directed towards the method a nuclear device was contained within a bomb. I don't know the answer to that.