what should I do to file a divorce?

You do not have to be in agreement to obtain a divorce. However, due to the contested nature of the divorce proceedings, you should be prepared for the divorce to be more expensive than one that is agreed. If you have children, then you need to hire an attorney. I do not suggest you try and represent yourself in a contested divorce with children. If you do not have children, you might be able to do some of the initial paperwork on your own. However, I would still seek out an attorney for some basic advice to get you on the right track and (if your matter remains contested) you will need to hire representation for your final trial.