After you’ve installed and opened the Google Hangouts app you should see a page similar to the one below-left. If you haven’t signed in with a Google account you will see a page like the one below-right. If so, sign in with a Google account (@gmail.com) to continue.
Once you are signed in, tap the plus button on the bottom right of your screen. Doing so will show a screen like the one below:
From here you can add your teammates by entering the Gmail account they used to sign into Hangouts. Once your group is set up you will be able to have a group chat/call with all members of your group.
If you are going to use Google Hangouts to communicate and coordinate tactics during a match, please set up your Google Hangouts beforehand to ensure you have the most gaming time possible!