"Dreams are coming true, and it sounds crazy, but it really feels wonderful," the actress said about moving from the stage to the big screen.
Erivo earned two Golden Globe nominations for Harriet including Best Actress in a Drama Film and Best Original Song for "Stand Up."
"It's overwhelming. I didn't expect that to happen," she said about the nominations. "Like to have two nominations, that's mad. It's been incredible."
Tubman was a former slave who joined the abolitionist movement and helped other slaves reach freedom. Harriet, from director Kasi Lemmons, hit theaters in November.
"I think that the most interesting thing that I learned about her was how much her faith played a part in her journey, her actual physical journey to freedom and her journey back and fourth to save enslaved people," Erivo said.
"That she was so close to God and her faith was astounding," she continued.