Former Boston Celtics player Chris Herren will be speaking about his experience with drug addiction Wednesday at 7 p.m. in the Acton-Boxborough Regional High School auditorium. The free event is sponsored by the Acton-Boxborough United Way in partnership with the Acton-Boxborough Regional Parent Teacher Student Organization. Herren, who grew up in Fall River, is a motivational speaker who discusses his personal struggle with drug and alcohol abuse during his time as a top collegiate player and his professional basketball career.