Download the SSH Credentials Plugin. Then create an SSH Username with private key credential with Global scope.
Fill in the private key field with a private SSH Key if you wish to authenticate SSH with keys; you must leave the passphrase
section blank. Your keys will need to follow the OpenSSH PEM format. See RFC 4716 for more information.
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----