First thing I'd do is google for the Ohio state affiliate of the USCF... here is is:
They should have a tournament listing somewhere.
You need to be a USCF member to enter by the way... so maybe that's actually the first step. You can pay online and become one. If you're already one you can look in the back of the magazine for a listing of your state's tournaments.
Then you just show up on the day it says, in time for the registration (hours will be listed) pay the entry fee and the first round should start within an hour. Often you can pre-register for a small discount to the entry fee (tournament directors like to know how many to expect).
Tournament directors also like people to come to their tournaments. In the listing it should say the TD's name. You should be able to find some contact info on the site, if you have any questions they'd be more than happy to answer them I'd imagine.
I have never been in one and i would like to know how to enter one and what i need to know ect if anyone could help me it would be awesome