You will have to file an amended tax return for 2018 to add 2018 W-2's that you received. You should wait for the tax refund to be received before amending the tax return. Amended tax returns can only be printed and mailed, not e-filed.
The IRS will take up to 16 weeks or longer to process the amended tax return. After printing, signing, dating and mailing the amended return to the IRS wait for at least three weeks before checking the status of the amended return on this IRS website - https://www.irs.gov/filing/wheres-my-amended-return
See this TurboTax support FAQ for amending a 2018 tax return originally completed and filed using TurboTax - https://ttlc.intuit.com/questions/4667233-how-do-i-amend-a-2018-return-in-turbotax