This depends on which product you have. I use TurboTax Deluxe which I purchased.
So for me, I start the TT application and it says start a new return right on the first screen.
Each time you do something to your return, be sure to do a SAVE. Deluxe offers this option to save each time you close out your session in a normal way.
Start the tax return. Save the return with a sensible name. Continue using the return or stop Turbo Tax activity. Observe which disk the tax return is on...backup this file/library/disk somewhere.
When you continue using Turbo Tax it will help you to select your saved file and allow you to key in new/changed data.
When you're working in the tax return and wish to finish by filing, you can print it and/or file electronically or both.
Keep a copy of your tax file, maybe on paper also. This copy will be used in next year's startup for 2022 tax season.
