Step 1:
Login to your CEX.IO account.
Step 2:
Navigate to the transaction history page.
Step 3:
Update the filter to All currencies, All transaction types, and choose a date range that includes All of your trades.
Step 4:
Click the Download CSV button on the bottom left of the page.
Step 4:
Upload your CSV file into the CEX.io tab of CryptoTrader.Tax