Short answers, pulled from the story.
The Einstein, Szilard letter was a document signed by Albert Einstein on the 2nd of August 1939, warning President Franklin D. Roosevelt about the possibility of Nazi Germany developing atomic bombs. Leo Szilard dictated the English version and enlisted Edward Teller to drive while they arranged for the letter to be delivered via Alexander Sachs.
Otto Hahn and Fritz Strassmann reported the discovery of nuclear fission in uranium on the 6th of January 1939. Lise Meitner identified this process as nuclear fission five days later in a February 11 issue of Nature.
Officials denied Albert Einstein clearance needed in July 1940 because his pacifist leanings and celebrity status made him a security risk. He had no knowledge of atomic bomb development and held no influence over decisions regarding its use.
Adamson authorized $6,000 for purchasing uranium and graphite, which equals roughly $100,000 in current USD. This amount was approved by the Advisory Committee on Uranium when it convened for the first time on October 21.
After meeting with President Roosevelt on October 11, Alexander Sachs secured an invitation to breakfast the next morning where he persuaded the president to take action. Roosevelt declared that the letter required action and authorized the creation of the Advisory Committee on Uranium.