You have to specify the type of connection protocol with the URL (http or https). Otherwise the connection will fail. Futhermore, we recommend to use a fully qualified domain name (FQDN) instead of hostnames only.
If your Jira installation uses a special port you also need to specify the port number. Append the port number at the end of the URL separated by colon (e.g.,
https://jira.example.com:8080). Ask your Jira administrator if you are not sure about URL and port number.