Moyes also managed the 28-year-old during his time at Everton and believes he can get the best out of the England striker.
"I've been fortunate, I've known Wayne since he was 16," Moyes said.
"I've had several meetings with Wayne. He's training brilliantly well, he's come back in good shape and I'm really looking forward to working with him.
"We have spoken several times and as far as I've seen it, whatever happened before has gone.
"We are working together now. I see a glint in his eye, he looks happy and if he is saying I'm going to knuckle down and get it right - let's not kid ourselves.
"He's a terrific player and let me reiterate, he's not for sale."
Moyes also distanced himself from any meeting between Rooney and his predecessor Sir Alex Ferguson about a possible departure for the forward from Old Trafford.
"There was a private meeting between two people and I was not privy to that. I'm now looking at it in my period at Man Utd," Moyes said.
"I'm really looking forward to working with Wayne and getting him to the levels I know he's capable of. I can tell you categorically that Wayne Rooney is training very well.
"If I was Wayne, you look at the legends that have played for this club. I could see George Best, Bobby Charlton, Roy Keane and I thought Wayne isn't too far away from that.
"It's not too difficult to get the goals and he could be near to that."