"Divorced" is not a filing status. Depending on whether you have primary custody of any children involved, you now file as Head of Household, or if no children--Single. You change your filing status in My Info. But before you do that--if you are using an old account that was previously used for a joint return, it would be better by far to start over in a new account with a different user ID. It is too messy to remove a spouse's data from the account if you are not filing together now.
And...was the divorce final by the end of 2018? You can only file Single if your marriage ended before the end of 2018.