Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
where the username:password are Base64 encoded.

In this example, the url has been changed to one that is protected by HTTP Basic authorization.
Mode to Secure.Mode is set to Insecure, the HTTP client will fail to send with this error message: Exception occurred, Failed to build request BasicHttpAuth requires HTTPS and HttpClient Health displays:

BasicHttpAuth from the Auth Type drop-down list and click SaveConfig options.
Username And Password credentials and click Save.