Check to see if you are already registered https://voterlookup.ohiosos.gov/voterlookup.aspx
To use the online voter registration system you must have a current Ohio driver’s license or Ohio identification card number, name, date of birth, address, and last four digits of your Social Security Number.
Online registration form (in English and Spanish): https://olvr.ohiosos.gov/
You declare your political party affiliation by requesting the ballot of a political party in a partisan primary election.
If you do not desire to affiliate with a political party in Ohio, you are considered to be an unaffiliated voter. An unaffiliated voter does not vote the ballot of a political party in a primary election. However, an unaffiliated voter may vote the Official Questions & Issues Ballot, if there is one for the voter's precinct at the election.
Voter registration deadline is no later than 30 days prior to an election:
Election Calendar: https://www.ohiosos.gov/publications/2020-elections-calendar/#gref
Ohio does not offer same-day voter registration
To update registration after a move or name change, use the voter registration form.
County Boards of Elections Directory: Each of Ohio’s 88 counties has a Board of Elections (BOE) office that is responsible for administering local elections. For addresses and contact information see https://www.ohiosos.gov/elections/elections-officials/county-boards-of-elections-directory/
To cancel your Ohio registration complete the voter registration cancellation form and mail it to your county board of elections https://www.ohiosos.gov/globalassets/elections/forms/10-a.pdf