If you are seeing "Ready to mail," it means you
chose the File by Mail option instead of e-File or your
return is not eligible for e-filing. So you will need to print and mail your
return if you choose to file a paper return or if your return is not eligible
for e-file.
This link will give you the instructions on how to print and
mail if you are using the TurboTax Online version of the software https://ttlc.intuit.com/questions/1944348
If you chose the File by Mail option by mistake, you can switch
to e-file using the steps below. Click on "Change to e-file
your return in TurboTax Online versions" below and it will show
you the instructions for how to do that.
NOTE: If you try to switch to e-file and it
doesn't allow you to, you can find some reasons listed here https://ttlc.intuit.com/questions/1901497 that would be the cause for not being
able to e-file your return. And in this case, you need to print and mail.
https://ttlc.intuit.com/replies/3985787