To get started connecting with SFTP please download winscp and unzip/install the program. In this guide you will be connecting to a linux server behind a bastion server. A bastion host is a server whose purpose is to provide access to a private network from an external network, such as the Internet.
Launch winscp and select SFTP connection from the drop down.
Enter the Target servers Host name, User name and Password or optionally key. The Target server is the one you hope to connect to after logging into a bastion server. Since the connection will be SFTP, you will use port 22. See the next section to configure ssh key based access.
To configure a tunnel with a private key, select Advanced.
Select SSH -> Authentication and load the private key file used to SSH into the target SFTP instance, not the Bastion Host server. **NOTE: the key should be in the putty .ppk format file extension.**
Next, Select Connection -> Tunnel and check Connect through SSH tunnel. Enter the Hostname as the IP address of the bastion server with port 22. The user name on the bastion server and the target SFTP server should be the same, and be authorized to the use the SSH public/private key pair already. Select the private key to be used for both the bastion. Select OK.
**NOTE: the key should be in the putty .ppk format file extension.**