Filezilla SSH - cPanel Instructions
Set Filzilla to SSH/SFTP using the site manager.
Set to use authorisation by Key File
For me I had to go into cPanel and then create a key. REMEMBER your password you need it in a minute.
Then "authorize" my key.
Convert your key to PPK in cPanel. You need your password.
Download it & save it somewhere you remember.
Use the Browse option in Filezilla SFTP settings and then upload it.
Then I also had to change my "username" in Filezilla from id_rsa to my cPanel account name. After that things worked well.
As an additional note, instead of using my remote directory as /public_html/ which I would for FTP I had to change it to the full directory /home/YourCpanelUserName/public_html
Hope that that helps someone.