only a Corporation, Partnership, or Trust files a tax return using Turbotax business. if your's was a sole proprietorship (SP)you need one of the desktop 1040 apps.
if your business is other than a SP you need to file a business return and then, except for a C-Corp, include the business K-1 in your 1040 return. if you filed your 1040 already and it was accepted you'll need to amend
you can purchase Turbotax business through an online retailer like Amazon or Walmart. Maybe someone can supply a direct link to the Turbotax website where you can download the app. if you prefer
Do you need to buy it? To do a prior year Business or Estate/Trust return you have to buy the Desktop program here,
https://turbotax.intuit.com/personal-taxes/past-years-products
Business is only available for Windows not Mac. Windows System Requirements
https://turbotax.intuit.com/personal-taxes/cd-download/tta-system-requirements