How did the American people find out what happened at Pearl Harbor

Mainly through radio broadcasts.

Explanation:

The Pearl Harbor attack happened on the 7th of December, 1941. News reached the White House and was relayed to the public for the first time by RuthJane Rumlet, working for the White House Press secretary at the time Stephen T. Early. The new reporters then relayed this back to their new stations. They mainly provided newspapers that were published the following morning. However, in 1941, about 41million radios were in American homes and the news was primarily broken to the public via emergency broadcasts, outside of normal news broadcasting time. In areas where many people gather the news was announced them over a speaker. An American football game was even interrupted to break the news to the stadium.