How does one enter a prior year tax return? I lost my 2023, so when turbo taxing my 2024, it says i can enter the data manually for the prior year.

You would only be entering data relevant to this year.  If you had a capital loss carryover or something of that nature.  The system will prompt you with questions as you go through.

@mang108 

I think it's saying you can enter all your 2024 info manually.  So you will be starting over entering your name, address, ssn then income and deductions, etc.  

Did you use the Desktop program for 2023?  If you used the Online version it should still be there.  How did you lose it?  Maybe you have another account?

How to view all your accounts
https://ttlc.intuit.com/turbotax-support/en-us/help-article/account-management/many-intuit-accounts-turbotax/L9aVfKS1Z_US_en_US?uid=ll5g6zcx

It's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
https://myturbotax.intuit.com/account-recovery/

If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online.

You can also request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript