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.

Do not password protect your SSH key.

Example private key format:


        -----BEGIN RSA PRIVATE KEY-----

        MIICXAIBAAKBgQCI2WI1RnM0GGDPRc3pRk3AZxs7ZqY1FDz1lpOsgquxvb36b7G5
        16v+G/3vduBs0tmfbbsA2jop2PZ1dwPlth1GeEJY6ne/kapvkG+hjcoghDzUu3PE
        3Vwgd48IU7MADuBxBn28D8eUlH94FR5sCojl1NeZ3F1GGtbgiIHG3Zyr2QIDAQAB
        AoGAfsWaQ64StLTModaRbMMy7cTWJk3uNIed/QfTn2ChexNBtYjZBEb1zn3R3I6s
        UkN1VEqLjLucW/3gOmrZUmhFbwUpfivI61BdDeDXkqMO9/n9t3RaZciSCTlnRL+s
        7OGHSu/XnqIrDtG4jEx09F1nOO+O1TQvSaY8Z+Mrdw5tPP0CQQD3q7ElJBr7Xi7o
        JT9Ho68sI2zi+FXq4x5+7BbeNFTv8GrH0MviGatbLjdi18FHvaxDflrDtwvtLGY+
        DTgbXOLbAkEAjXOUVs6COEW5Xoe44M2whNXi0A25BaR+0UEx/MJqcXY9bZ4hoOkN
        88hQum8td/hjdRbbBXPtTTGm4lxClJKYWwJBAMAvm9OtU76xFAcSOCt4Kcs/ZhQu
        DkWpnhVxUEF3LF3QGpwZOsyljKHBmDr8H0BzP4RUPUxX80pExMXr7hjVmDcCQA8R
        QbrhcoOWAcHtCSeBIY10zx1EaPIN7KhTnoSDHR2K784uavyd9quCKf9B+oDuB4Ig
        diIlkCCJ6nHwS/NRjkMCQAZ61YhY8jhkCBONrFfx9pdXNIzQF5NCxShMm79gDnp9
        wjWcyy7pIUfBrtiZCuojGGTdNBhvG20ohMp/lfs52Hg=

        -----END RSA PRIVATE KEY-----