Wish me luck. They said I'll for there for at least a couple of months
Try not to be scared; everyone there will want to help you, it's why they're doing it. Be open with folk; it'll make your experience and theirs better, as well as help you to recover faster.
I was put as an inpatient in the psych ward for four days because my Mom thought I was suicidal. To be honest, I could barely take it four days, let alone a couple months.
But a psych ward and an anorexia treatment center are probably different. What they'll most likely do is monitor your behavior very closely, your interactions with others, and make you eat in front of them. You probably also won't be able to go to the bathroom directly after so they can see you hold down your food.
If you're going for a couple months, I think you are allowed to bring your own clothes, but at times you will have to wear gowns and other materials they give you. I'm not sure if you're allowed an iPod or music of any form, but you could try to bring that. You can't bring anything that can be used to kill yourself with, so don't bring anything sharp or they will confiscate it.
You're not allowed to bring your cellphone, so I wouldn't think about that. I hope everything works out for you, and please, for your sake, get better.