Investors & landlords

Search for sale of business property (copy an paste if needed).    Then you should be able to edit your entries.   Are you using the desktop software?   If so, click on Forms to see all of the forms included with your return.   If you are using TurboTax Online, you will need to go through the Print Center (Tools menu) to view your forms to see the data flow.  

How do I edit or delete the sale of a business property I've already entered (Form 4797)?

Check the Rental Properties and Royalties section also, specifically the Assets section.   To get there, search for rentals, use the Jump to link, and choose Edit.  Then scroll down and update the Assets/Depreciation section.