In order to add a Poloniex Exchange ledger, you must first download your transaction history from your Poloniex account. Your complete history is made up of 3 separate files: Deposit History, Trade History and Withdrawal History
Log-in to https://poloniex.com
Download Deposit & Withdrawal History files
Click on Balances > History
Click "Export Complete Deposit History"
Scroll down to the next section and click "Export Complete Withdrawal History"
Download Trade History file
Click Orders > My trade history and analysis
Click the "Export History" button
Select history type (in this case it is "trade") and input your date range. Then click "download".
You should now have 3 separate files. Now you are ready to Upload your transaction data to create a new Poloniex exchange ledger.