Head to the Blockonomics site. Once you've logged in, select Wallet Watcher at the top of the screen.
Here you'll see a running balance of your imported Bitcoin/Bitcoin Cash addresses. On the dashboard menu, select Export. This menu allows you to export a CSV of all your historical transactions for your imported addresses.
Next, select a date range for your CSV. Be sure to select as wide of a date range as possible to ensure that CoinLedger has an accurate picture of your transaction history.
Additionally, be sure to check Show fiat value at time of transaction.
Then, click Export to CSV to generate and download your file. Make sure that you select the CSV file option and not the Excel file option.
Once you've downloaded the file, head to CoinLedger and add a Blockonomics account by clicking Add Account > and searching for Blockonomics.
Click on Upload File and drag your Blockonomics CSV files into the box to seamlessly import your transactions. Each of your transactions will now import.