In order to import Accounts go to Accounts. Click on Action -> Import.
Below screen will pop up: You can import from supported gateways, CSV, Excel and QuickBook
If your gateway is supported you will see that here. Select from where you want to import and click Next. If importing from Excel or CSV below screen will be displayed: Upload file and setup mappings.
For other sources list of Accounts will be displayed which are not setup in Neon. Select accounts you want to import and click Import. Job will be logged and you will be notified when accounts will be imported.