Open Google Chrome and click on the Google Apps menu > Google Hangouts. Go to the Conversations tab and start a new chat.
Click on the Menu button displayed at the top-right corner of the chat window and select New Group Conversation.
Type the names of the participants in the Search for people field and click on Add people:
Click on the Menu button displayed at the top right corner of the group hangout window and select Options. Here, you'll find a host of useful settings to customize your hangout session (change group name, archive conversation, or leave group):
Group Hangout with Google Hangouts
Open the Google Hangouts app, tap on + to start a new conversation and then select New Group:
Type the name of the participants or select them from your address book.