HouTx gives you some excellent advice. I am a correctional DON. I came into a facility that was known systemwide as a place to avoid. When I accepted the job, three people openly questioned my sanity. No one wanted to work here. When my boss briefed me on the situation, one thing became abundantly clear: A significant portion of the issues were the direct result of the attitude at the top, something I could change.
As HouTx advised you to do, I spent time getting the lay of the land, figuring out what (and who) was working and what wasn't, and then I set out to make gradual changes. I solicited staff input, which the previous manager had not done, so sure was she that she had cornered the market on the only "right" way to do everything. I found out that a lot of the problems led back to the philosophies of my predecessor. People were used to being yelled at and dictated to, and very little respect was shown. The medical department was also at war with pretty much every department in the facility, as her dictatorial ways extended well beyond the boundaries of the medical unit. Instead of coming up with cooperative solutions, her approach with other department heads was pretty much, "We have a problem, and here is what you are going to do to fix it." Other department heads found it incredibly insulting to be talked down to and dictated to by another department head, and understandably so. Once I found this out, I met with each department head and I assured them that if there was an issue of mutual interest, we would sit down together and come up with a solution that we could both live with.
Employee morale was in the toilet. Staff was used to being yelled at and belittled. The first three weeks I was here no one came in the office, because they were used to only bad things happening in there.
I have now been in this job for almost seven years. Most of the bad apples have moved on, their opinions and methods no longer finding an audience. We have a strong cooperative working relationship with the other departments and with administration. I have a waiting list for transfers in, which would never have happened when I got here.
Remember that change, even when it is positive, creates stress. Go gradually and address problems as you find them. You aren't going to fix everything at once - nor should you try to. Trust the people around you, and give them credit for their skills and experience. Solicit employee ideas, and implement the good ones. Show employees proper respect, but make it plain what your expectations are.
Good luck to you, and welcome to management.