If you filed a 2018 tax return and it was accepted by the IRS then you do NOT refile. You amend the original tax return that was filed to make any type of correction. An amended tax return, Form 1040X, can only be printed, signed, dated and mailed by you to the IRS. You do not start the amend process until you have received the tax refund or the tax owed and paid have been processed from the original tax return.
See this TurboTax support FAQ for amending a 2018 tax return originally completed and filed using TurboTax - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-a-return-in-turbotax/01/27579
