What business tax return do you need to file? If you need to file a separate Business return like for a 1065 Partnership or LLC or a 1120 including a Single Member LLC - S corp or a 1041 Estate/Trust return you need Turbo Tax Business in addition to a personal tax program.
Or are you self employed, sole proprietor, Single Member LLC, Independent Contractor, etc? Those are filed on Schedule C in your personal 1040 return.
You might need Turbo Tax Business, not to be confused with the personal Home & Business version. Home & Business is just for personal returns that need schedule C for self employment. TT Business is not available to do online or on a Mac. You can buy the Windows Desktop program here,
https://turbotax.intuit.com/small-business-taxes/cd-download
You can have both a personal program and the Business program installed on the same computer at the same time.
If you mean you had self-employment earnings to add to your personal tax return, you will need to amend the return you filed to add your business receipts and expenses. You will see an option to amend your return when you log into your TurboTax program.
If you mean you have a partnership or corporate return you need to file, you can do that separately from your personal tax return by downloading the TurboTax Business product. If you prepare an S corporation or Partnership return, you will generate a Schedule K-1 that you will use to enter you share of the business income and related items on your personal return, so you may need to amend your personal return to do that.