Did you already e-file? If you already e-filed you cannot cancel it.
You cannot change or add anything on the return that you just e-filed, nor can you stop it. It is too late, just like when you put an envelope in a US mailbox on the corner. The IRS does not allow you to take it back.
If you have not e-filed, then clear out your data.
CLEAR AND START OVER
https://ttlc.intuit.com/turbotax-support/en-us/help-article/change-service-level/clear-start-turbotax-online/L37BZFuBV_US_en_US?uid=m6b26ost