How do I import tax returns for previous years from my computer to my TurboTax account online? My previous returns were done using TurboTax software. Thanks.

To transfer a 2024 tax return from TurboTax Desktop to TurboTax Online, follow the instructions below from this TurboTax Article

You can transfer your tax data file (with a filename extension .tax[year], such as .tax2024) only if you're switching a prior year return.

• You can't transfer your current year return.
• You won't be able to transfer a PDF, it must be a tax data file with a filename extension .tax2024.
• Remove any password protection from the data file before transferring. Follow these instructions.

Here's how to transfer:

You have to use TurboTax Online on your computer to do this transfer (it won’t work from a mobile device).

Note: If your TurboTax navigation looks different from what’s described here, learn more.

• Sign in to TurboTax Online and start a new return, or open and continue a return you already started.
• On Tax Home, select Start or Continue to enter your return. 
• Select Tax Tools from the left menu, then select Tools.
• In the pop-up window, select the Transfer last year's TurboTax return from your computer link (if you don’t see this option, you may need to clear and start over).

Follow the instructions to finish transferring your file.

Switching from TurboTax Online to TurboTax Desktop? Follow these instructions.

Or do you want to upload them to your online account to store them in MyDocuments?  You might be able to save the pdf files there.  

How to upload to Documents
https://ttlc.intuit.com/turbotax-support/en-us/help-article/small-business-processes/docstm/L0VlCWX5G_US_en_US?uid=lfuovrq8