The IRS thinks it was your 2019 return. So you need to Amend it and take out the 2018 W2 and enter the 2019 W2 and change any other wrong info on it.
How to amend an Online return
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/
Amended returns can only be MAILED not efiled. Don't mail the amended return until you get the first wrong refund. Then the amended return is only for the difference you get or owe back.
Then do you still need to do 2018? Or need to add this W2 to your 2018 return?
To do 2018 you have to buy the Desktop Download program here
https://turbotax.intuit.com/personal-taxes/past-years-products/
Or If you have a simple return You can fill out the blank forms for free.
Here is the IRS 2018 Form 1040
https://www.irs.gov/pub/irs-prior/f1040--2018.pdf
And instructions https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf
2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf
IRS 2018 Schedules 1 thru 6 (only if needed)
https://www.irs.gov/pub/irs-prior/f1040s1--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s2--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s3--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s4--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s5--2018.pdf
https://www.irs.gov/pub/irs-prior/f1040s6--2018.pdf
Don’t forget your state. And you will have to print and mail your returns. So be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.
