You used the online program and entered 2018 income instead of 2019 income and information? Hopefully the return will be rejected. When it rejects, clear out all of the 2018 data you entered. Then put in your 2019 data and re-file. You will not have a 2018 AGI. You can try to use "zero" but if zero does not work you will have to print, sign and mail 2019.
If the return is accepted, you have a bigger problem. Post back for help if that happens.
Do you need to fie a 2018 return?
Online preparation and e-filing for 2018 is permanently closed.
To file a return for a prior tax year
If you need to prepare a return for 2016, 2017, or 2018 you can purchase and download desktop software to do it, then print, sign, and mail the return(s)
Remember to prepare your state return as well—if you live in a state that has a state income tax.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Note: The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac. It cannot be used on a mobile device.
If you are getting a refund, there is not a penalty for filing past the deadline. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.
Then you have to WAIT for the return to be fully processed and receive the refund. Then you prepare an amended return on a Form 1040X. Form 1040X is not yet available--it will be available later in February.
A 1040X cannot be e-filed. It must be printed and mailed. It will take about 4 months for the IRS to process an amended return. It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.
Wait about 3 weeks from mailing and you can check the status of your amended return: