The four freedoms are freedom of speech, freedom of worship, freedom from want and freedom from fear
Freedom of speech was historically not given to African-Americans because they were not allowed to organize or hold public appearances or fight for their rights publicly because they would easily be arrested for it. Anywhere where they started preaching for their rights they would get arrested or beaten by the police or attacked by people.
Before African-Americans became predominantly Christian, many of them held their own beliefs which was based on oral tradition and things brought from Africa. These practices were forbidden and they would be severely punished if they were caught practicing anything that wasn't Christianity. This sometimes even included death.
Freedom from want was one of the biggest issues. They weren't allowed to educate themselves and get regular jobs because of segregation so many of them lived in extreme poverty. Many died of starvation or similar things because they couldn't afford to buy anything, or if they could nobody wanted to sell them anything.
Freedom from fear was also extremely important. Many African-Americans lived in constant fear of getting attacked because severe punishment that included even mutilation or death by lynching was a common thing for any African-American that lived in the South. They lived in constant fear and if they wanted to change anything the fear would stop them from fighting for it.
