Update WinSCP doc for clarity now that SSH key auth is required

source/content/guides/sftp/06-winscp.md

@@ -19,13 +19,25 @@ This section provides information on how to use WinSCP with Pantheon.
 
 ## Before You Begin
 
-- Make sure you have the Pantheon SFTP connection information for your site ready. Refer to the documentation on [how to find the SFTP credentials](/guides/sftp/sftp-connection-info) for your site if you need to locate the connection information.
+- Make sure you have the [Pantheon SFTP connection information for your site ready](/guides/sftp/sftp-connection-info). You will need the hostname, username, and port.
+
+- [Generate an SSH key for authentication](/ssh-keys#windows) and [add it to your Pantheon dashboard](/ssh-keys#add-ssh-key---new-dashboard). You must use an SSH key to authenticate, dashboard credentials will not work.
 
 - [Download and install WinSCP](https://winscp.net/eng/docs/installation#download) if you haven't already.
 
 ## Connect Your WinSCP Client to Pantheon
 
-1. Start the WinSCP application and enter the connection information. Be sure to take note of the port as Pantheon uses a **non-standard port** for SFTP.
+1. Start the WinSCP application and enter the connection information. Be sure to take note of the port as Pantheon uses a **non-standard port** for SFTP. Leave the password field blank.
+
+  ![WinSCP connection details with filled out host, username, and port](../../../images/WinSCP-connection-details.png)
+
+1. Click the **Advanced..** button under the password field, then select **SSH** > **Authentication** from the left-hand navigation menu and provide the path to your private key file.
+
+  If you specify a key in an unsupported format (e.g., OpenSSH) you will be prompted to convert the key to PuTTY format, if prompted to convert respond by clicking Ok.
+
+  ![WinSCP unsupported key prompt to convert to PuTTY format](../../../images/WinSCP-convert-key.png)
+
+  Click Save and Ok, then click the Login button.
 
 1. Click **Yes** to accept the server's host RSA2 Key Fingerprint for the current session and store it in the cache. This allows you to connect to the server and manage your files for the current session.