You can't just switch the order of names. You would have to clear and start over. It shouldn't make a difference who is listed first or primary. But the IRS does want you to be consistent each year.
to clear and start over
Why do you want to do that? It makes no difference to your refund or tax due. And the IRS prefers for you to stay consistent from one year to the next when you file joint returns. Switching the order of the names can cause confusion and delays in processing your tax return.
If this is your very first joint return, you can clear it and start over. You cannot just swap the names with each other because the accompanying data that was entered will not move with the names. If you want to clear and start over, then you can do that, and enter the "primary" tax payer first when you begin to enter information in MY INFO.
CLEAR AND START OVER
https://ttlc.intuit.com/questions/2586254-how-do-i-clear-and-start-over
Attempting to switch the order of the names on an existing tax return will cause errors that you will not be able to fix. That's why the other replies are telling you to clear your tax return and start over. The primary taxpayer has to be the first name that you enter when you first start the tax return. You can't change it later.