Keep the test report, then have a licensed mitigation specialist inspect the house and write a proposal. Ohio requires that inspection and a floor plan before any written quote, and a signed proposal before work starts.
More detail
If the seller gave a credit instead of installing a system, the scoping is now yours. Ask for an Ohio-licensed mitigation contractor and specialist, and check both licenses on ODH's Hire a Professional page. The proposal should list both license numbers, the planned scope and completion date, the installed price, an estimate of annual operating cost, and either a guarantee to bring the average below 4 pCi/L or an explanation of why there is none. Keep living in the house normally in the meantime; radon risk builds over years, not weeks. After the install, schedule the post-mitigation test between 24 hours and 30 days after the fan starts. Our guide to checking an Ohio radon license covers the paperwork, and you can contact us to get the visit on the calendar.