SFTP is also known by its original name: SSH File Transfer Protocol. That's the SSH protocol - Secure Shell, a protocol used to move files. SFTP was developed in the 1990s. And it allows to move files securely.
SFTP Client is a piece of software that uses the SFTP protocol to securely transfer files to remote computers.
Download and install at: https://filezilla-project.org/download.php?type=client
From the menu select "File > Site Manager"
Click "New Site" to create a new site
Configure as shown below, note:
protocol: select SFTP
⑤ Logon Type: select key file
⑦ If you don't have a Private PuTTY Key, see the instructions here . Then click Connect.
Done, you can upload the file to your server.