Okay kiddo, so there was a time called the Great Depression when lots of people in America were really struggling to find work, make money, and afford the things they needed. It was a very scary time for many families.
But then something called World War II happened and lots of people had to fight in it. They were also scared because they didn't know what would happen to them or their loved ones.
The government of America wanted to make people feel safe and not so scared. They did things like making sure everyone had enough food to eat, giving jobs to people who didn't have them, and making sure the country was safe from enemies.
They also got people to work together and be kind to each other. And in the end, the war was won and things got better for many people. That's what "freedom from fear" means - feeling safe and not scared during a tough time.