You can buy Turbotax for up to 3 years past, which must be downloaded and installed on your own Mac or PC. 2021, 2022 and 2023 are available for purchase.
https://turbotax.intuit.com/personal-taxes/past-years-products/
For 2024, you can purchase the 2024 software to install on your own computer, or use the Online version.
For older than 2021, you would need to download the forms and instructions from the IRS website and prepare your returns by hand, or see a tax professional.
For most tax returns, you can do your back returns in any order. But if you have items that might carry forward (like business expenses, depreciation, or capital losses), you should work oldest to newest.
