What is your advice to help my oldest daughter deal with a new sibling?

I have 3 daughters ages 8, 6, and 4. I recently had a little boy who is 9 days old. My oldest daughter has been acting up since we brought her brother home from the hospital. She's been punching and bullying her other sisters and has been playing tricks on everyone. I've tried sitting her down and talking to her straight up, I've tried threatening her. She keeps doing really bad things. How do I handle this? What do I do?What is your advice to help my oldest daughter deal with a new sibling?
I have 4 kids of my own 10 year old boy,7boy,6,girl and 19 month old girl.one of the first things i did was to make my oldest my helper not for his brother and sisters,but for me and baby,just having that time with him and the baby was magic even if was just at feed time!you have to remember that she had you all to her self once.im sure she would love to have that time with just you,to talk about school,friends and how shes feeling.What is your advice to help my oldest daughter deal with a new sibling?
Chris did this when he was little, he simply wanted attention and its hard to be the oldest. Let her help with the baby, and when you can take her out and spend some time with her.
Let her be the helper
i would say involve her in the baby's life, and baby her too.