Jenkins uses this access key ID and secret access key to interface with Amazon EC2. If you have already signed up on EC2, you can obtain this from here. Otherwise, you need to sign up to Amazon Web Services to get one.

If no access key is set, implicit authentication mechanisms are used:

• Environment Variables - AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY (RECOMMENDED since they are recognized by all the AWS SDKs and CLI except for .NET), or AWS_ACCESS_KEY and AWS_SECRET_KEY (only recognized by Java SDK)
• Java System Properties - aws.accessKeyId and aws.secretKey
• Credential profiles file at the default location (~/.aws/credentials) shared by all AWS SDKs and the AWS CLI
• Instance profile credentials delivered through the Amazon EC2 metadata service (IAM role defined at the ec2 instance level)