Congratulations!
TurboTax doesn't have a feature that allows you to merge two previous accounts and start a new joint return.
You will be able to transfer one of the 2021 returns into a new return for 2022 and manually add the spouse. It makes sense to transfer the most complex return, but do note that whoever is transferred becomes the "taxpayer" and whoever is manually entered as the spouse in the interview becomes the "spouse." You will not be able to change this designation, and it really doesn't matter who is named taxpayer and who is named spouse.
In the interview, there is a section "My Info," and you have to answer the question "Were you married?" If you click the button for Married, then a drop down will appear that asks, "Do you want to file this return together with your spouse?" Choose "yes" to file a joint return. Then enter your spouse's information. This tells TurboTax to ask about the spouse's income and deductions as you proceed and to prepare a joint return.
