Reset books to re-import from Invoice

Reset books to re-import from Invoice

i set my Zoho Books to import from Zoho invoice over a year ago to "demo Books" - I never got around to it and now I am ready to actually just switch over to Books from Invoice - but when I try to "import Invoice" I'm told it's already been done... but it's all old stuff in there.

How can I reset my Books account to blank so I can start over?

Thank youl.