TurboTax does not support tax year 2018. You will need to locate a local tax professional to amend the 2018 tax return to add the W-2.
For tax year 2020 you will need to amend the return you filed to add the W-2.
See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...
