involved in a lawsuit for an unpaid credit card, what is the process for responding under OH state law

I would suggest two things:

First and foremost, I would recomend talking to an attorney in your area to discuss your options, what you should and should not say, etc.

If you decide to go at it alone, the following may be helpful.

1) Contact the court clerk where the law suit was filed and obtain the pleadings. Most jurisdictions require the attorney to provide their contact information on their pleadings filed with the court.

2) Contact your states Secretary of State and find out the contact information of their registered agent for the state.