Google Contacts (Your Groups)

Go to your waffle in the upper right hand corner - look for Contacts

On the left side there is a section called Labels - click on the plus to create a new "Label" - Give the label a name.

Now search for a person with the top search bar. Click on their name. This will show you what labels you have for them already. Click on the pencil to add a new label. After you click on the label you have to click apply

When you type in the label name it will pop up - click on the label to insert all of the email addresses associated with that label.