[keycloak-user] Adding new security-realm using CLI

I intend to use SSL for my Keycloak Server. So I am following the documentation from Keycloak for it. At one point they mentioned have to add a new security-realm using the CLI. But I have no idea how to use the CLI to input this /core-service=management/security-realm=UndertowRealm:add() It keeps saying it is not a recognized command. Any ideas? Regards, Kunal