Am filling out TT now. Made error in Sch C, car mileage year total. I can't find a way back to it, nor find the document itself. How do I change my entry in Schedule C?

You need to be looking at the Vehicle expenses under your Self-employment income.  To do this in TurboTax Online please follow these steps:

1. Open or continue your return in TurboTax
2. Search for self employment income (use this exact phrase, don't add a hyphen) and select the Jump to link at the top of the search results
3. Answer Yes on the Did you have any self-employment income or expenses? screen
   • If you land on the Your 2021 self-employed work summary page, select Review next to the work you're adding income for
4. Scroll down to Vehicle expense and click Edit