The first step is either to hire an attorney, or, file a petition for divorce on your own. If you have access to the bank account, get the money necessary to file and see an attorney as you may qualify to receive temporary spousal support, but, you must first have a court date and a hearing to get it. As well, you want to be able to stay in the house, assuming you have no other place to go. An attorney can help you protect your interests and your rights.
That's correct, filing a petition for divorce is the first step. If the two of you agree on the divorce, you can accomplish the divorce relatively cheap. Generally, the more contested a divorce is, the more expensive it is. In some counties, you can file an affidavit of inability to pay, sometimes called a "pauper's oath", which waives the court costs. If you proceed pro se, (without an attorney) some counties have a department that will help you through the process. It is definitely best, and faster, to get an attorney.