I was only trying to get a quote for my taxes but accidentally sent it in so how do I cancel my taxes so I can add myself to my husband's?

How to file the tax return is obvious on the transmission page.

You complete your tax return by finishing all 3 Steps in the File section. In Step 3, to e-file your tax return, you must click on the large Orange button labeled "Transmit my returns now".

After completing the File section and e-filing your tax return you will receive two emails from TurboTax. The first email when your tax return was transmitted and the second email when the tax return has either been accepted or rejected.

If you actually transmitted the tax return and received an email from TurboTax acknowledging the transmission the return cannot be canceled.

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

You will have to wait for the IRS to start accepting or rejecting 2020 tax returns on February 12, 2021
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 1040X, can only be printed and mailed to the IRS if the original return was not e-filed. The IRS will take up to 16 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 on amending a tax return originally completed and filed using the 2020 TurboTax online editions - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/01/27577