To clear and start over, you first have to open your return interview.
Once the return is open, go to the left menu column and click on TAX TOOLS, then choose "Clear and Start Over."
See this FAQ and video first:
FAQ: How do I clear and start over in TurboTax Online?
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-onli...
