No one can give you step by step guidance without knowing exactly what TurboTax product you are using. What year are you working on? Are you using TurboTax Online or the CD/Download TurboTax software? And what edition: Basic, Deluxe, Premier, etc.? The steps are not the same in all versions.
Also, how are the sales that you want to modify getting into TurboTax in the first place? If you are entering the information manually, you would make the wash sale adjustments as you enter each sale. Or are you importing the 1099-B information from your brokerage? If you are importing it, I would expect the information from the broker to already include the wash sale adjustments. Or is the problem that the wash sales are across different brokerages, and the broker where you sold doesn't know about a purchase from a different broker? But it's not likely that you are importing right now. Most brokerages would not have their TurboTax import data for 2019 ready this early, and you cannot import 1099-B information for past years.
