How do I go back and change the filing status

Please explain----are you trying to make changes to a return that you already e-filed---or make changes to a return that has NOT been filed yet?

If you have NOT filed the tax return, click on My Info on the left side of the online program screen.  Edit your information to change from filing jointly.

If you have filed your tax return, you will have to amend the return to change your filing status.  You must amend your tax return on or before April 15, 2025 to change from joint to separately.

Once a tax return has been filed it cannot be changed, canceled or retrieved

You will have to wait for the IRS to either Accept or Reject your filed federal tax return.
If the return is rejected you can make the necessary changes and e-file again.
If the return is accepted you will have to amend your original tax return. An amended return, Form 1040-X, can only be printed and mailed to the IRS if the original tax return was not e-filed. The IRS will take up to 20 weeks or longer to process an amended tax return.

Before starting to amend the tax return, wait for the tax refund to be received or the taxes due to be paid and processed by the IRS.

See this TurboTax support FAQ for amending a current year tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-federal-tax-return-current-year/L7eS6o1qh_US_en_US?uid=lfunevhk