Harris, who is the club's record goalscorer following two separate spells at The Den, has revealed that he is relishing the opportunity to move into coaching.
"It is a different challenge and a fresh start," Harris told BBC Sport. "As much as I am coming back to a place I know well, I am going into the unknown a certain degree.
"Every day I will be learning and I want to learn, be a good coach and improve every day. Steve has given me an opportunity to learn from him.
"I want to be out on the grass and the training ground every day and be involved in a sport and a game I love."
Harris recently retired from playing after a stint with Southend United.