The 29-year-old Williams showed the girls the right way to hit a tennis ball. She also spoke about the importance of eating right and establishing healthy habits early in life.
"And we're teaching some new young people how to play and some people who have already played tennis. And it's just about teaching them how to be active and how to stay hydrated and how to really lead healthy lives," Williams said.
The tennis star recently wrote the book "Come to Win" about how sports helped shape the lives of 50 successful and famous people, including former President Bill Clinton, actor Denzel Washington, and designer Vera Wang.