*NOTE* It is important to upload the file EXACTLY as received from Bittrex. Do not open the file and use the "save" or "save as" function on your computer as this can affect the encoding of the file. If you need to edit your CSV, please use Google Sheets.*
Login To Your Bittrex Acount
On the top right of the menu header, select the "Orders" button.
Under the "Recent Orders" section, select "Download History".
Use the pop up to download trade history files from ALL years of trading. You will need to export a separate file for each year.
*CryptoTrader.Tax needs data from all years to build an accurate tax report.
Navigate to the Bittrex tab on CryptoTrader.Tax and import your CSV files from each year of trading.