A node id is both its address in Staex network and its public key. Such a tight coupling helps prevent man-in-the-middle attacks: spoofing node id amounts to stealing node's private key — something that should not happen under normal circumstances.
Node id is presented in the output of many commands as BASE32-encoded string. In this form node id can be used in place of a DNS name in any configuration file and any command that you type in a terminal. Make sure to execute this command from a host that runs Staex.