If you used the Desktop program last year here’s How to transfer into the Online version. You need to have the prior year .tax2023 file on your computer. Expand the link if you used the Desktop software last year........
https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/transfer-last-year-return-turbotax-online/L279eUvY2_US_en_US?uid=l8w7nlbv
Also be aware that if you have always used the desktop version, the Online version is not as fully-featured. For example, it has no Forms Mode (for viewing/editing the actual forms), can only prepare a single Federal return per account, and any state return (if applicable) has an additional preparation fee. There are also some form limitations depending on which edition of Online TurboTax you choose--Free, Deluxe, Premium, etc.