How to config a cluster?

Elastic Stack Elasticsearch
1

I try to start elastic search on both PC-A(172.16.40.20) and PC-B(172.16.40.199) with default setting (v-0.13), and then check cluster status, only show 1 node with yellow flag.

how can I config it? and I try to change the cluster name in elasticsearch.yml

cluster:
name:mycluster

and restart again, the cluster name still be "elasticsearch"

2

#1 was solved, add below in yml

discovery.zen.ping.unicast:
hosts: ["172.16.40.20:9300","172.16.101.52:9300"]

#2 is not solved.