Autism..Coping with behaviors

I have a beautiful smart 6 yr old boy who has recently been diagnosed with Autism. He's an awesome cool little kid but his behaviors are driving me insane. Screaming, yelling, punching things, says the most craziest things, etc. His 4 yr old sister who doesn't have Autism is actually starting to mimic some of his behaviors. He is beyond struggling with potty training. Still wears a pull up. has no issues whatsoever going to the bathroom in them. knows what and how to go to the bathroom appropriately. How have other moms with Autistic kids dealt with behavioral issues? how do you deal with the tantrums? the screaming? the back talking? TYIA