If you are looking for a law that says that you can carry a firearm openly, you won't find it. It does not exist in Ohio.
Start with Ohio Revised Code 9.68. It reiterates the Right to Keep and Bear Arms, prohibits local governments from making gun law, and specifically states that the only lawful gun law in Ohio is State and federal law. State and federal law do not list what you may do, only that which you may not do. Again, nowhere in those laws will you find a prohibition on carrying a firearm openly.
You will find Ohio law that says that you must have a permission slip to conceal the firearm. You will find a law that says you must have that permission slip to carry in you car. That law will tell you how to transport your gun in your car if you do not have the permission slip (basically, unloaded firearm in a closed container, loaded magazine in a separately closing container). You will find law that says without a permission slip, you may not carry in most places that sell alcohol or within 1000 feet of a school. You will find laws that bar carry in some locations with or without the permission slip, for example, courtrooms and courthouses.
But, nowhere will you see a law stating that you may not strap on a gun and walk down main street. You may even enter the premises of another while so strapped, as long as they don't have a prominently displayed gun-buster sign or don't ask you to leave.
However, do not take my word or anyone else's for what the law says. It is your ass that you are risking. Read the law for yourself.