Percona XtraDB Cluster using 2 Node and 1 Node as GALERA ARBITRATOR

I have setup 2 Node ( MySQL) Percona XtraDB cluster using instructions given on Percona site.
For 3rd, I want to use garbd ( Galera Arbitrator).

What is --group=

Is it name of wsrep_cluster_name=mysql_cluster in my.cnf ?

and also address , do I need specify MySQL 2 Node Cluster IP like in wsrep_cluster_address in my.cnf
garbd --group=example_cluster [COLOR=#4070A0][B][/B] --address=“gcomm://,,”
Any input is greatly appreciated. Thanks