Frederick Douglass attempted to address the needs of people of African descent in the United States by agitating for an end to slavery and for equal rights for African Americans.
Before the Civil War, the most important problem facing African Americans was, of course, slavery. Douglass, as an escaped slave, knew this very well. He attempted to promote the abolition of slavery by becoming one of the best-known abolitionist speakers in the United States.
After the end of slavery, Douglass pushed for equal rights for blacks. He tried to fight against the continuing inequality in the South by writing and speaking on the subject. He also took various posts that allowed him to try to help blacks in general. One of the most important of these was his post as a trustee of all-black Howard University.
In these ways, Douglass attempted to address the needs of African Americans both before and after the end of slavery.