How we can set 2 instance of MongoDB in same machine

Question

How we can setup 2 Nodes Mongo DB Cluster with the help of 1 Arbiter 

Node 1 : Mongodb1 (Primary)

Node 2 : Mongodb2 (Secondary) , Arbiter

(or)

Node 1 : Mongodb1 (Primary), Arbiter

Node 2 : Mongodb2 (Secondary)