1.Choose Tools | Profiles (Beyond Compare | Profiles on macOS) to open the Profiles dialog.
2.Select an Amazon S3 profile on the left pane or click the New button 
and choose Amazon S3 Profile.
3.Choose a setting from the Authentication type dropdown to control where credentials are loaded from:
oSaved S3 credentials: Use saved Access key ID and Secret access key.
oLoad from credentials file: Load the access key and secret access key from an AWS SDK credentials or AWS CLI config file. If provided, security tokens will be used for time-limited credentials. The default credentials file is %UserProfile%\.aws\credentials 
or ~/.aws/credentials 
, but Beyond Compare will use the AWS CLI "config" file if necessary and does respect the AWS_SHARED_CREDENTIALS_FILE and AWS_CONFIG_FILE environment variables if they're present. The profile should be one that exists within that file. If left blank, "default" is used.
oLoad from environment variables: Load the access key, secret access key, and security token from AWS_* environment variables. It will first check for the AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN variables. If those do not exist, it will select a profile from the default credentials file (as above). The AWS_PROFILE variable can be used to select a non-default profile.
4.Bucket (optional): Type the name of the S3 bucket you want to use if you don't have permission to list all buckets.
5.In the Description box, type any text you want to identify the profile.
