Short answer: You will need to make a new online account and start from scratch. You can't reuse an online account in which you previously filed as married.
Long answer: If you are the first-named spouse, the one whose name would go on the top line of a printed return, you can probably change from married to divorced by logging into your account using a computer and a web browser. You then have to make sure you completely delete any employers, income, deductions or other items that belong to your ex. It is highly recommended that you make a new account instead.
If you are the second-named spouse, you can't re-use this Turbotax online file and must create a new account to start over.