Just to clarify, the folder should be where you downloaded PHPMailer zip. Then use FileZilla with those settings to upload the entire folder:
FTP server: 185.27.134.11
Port: 21
Connection type: Plain FTP (not secure)
Username: you can find it on the Client Area, with the description as “Website for yoursubdomain”, where yoursubdomain can be overwritten with the name you’ve chosen during the creation of the account.
Password: click on the username, then scroll down and click “Show/Hide” to show the password. Then copy it and paste it in FileZilla.
Connect and go to yourdomain/htdocs/ and upload the PHPMailer folder that you’ve renamed there.