Contact groups are a useful feature that allow you to add several people to a conversation in just one click. Whether you need to cc a special board of administrators or address your whole support team, it'll make your life easier.
Create a group
Click on Contacts at the bottom left of your screen
In the menu that opens, click on Groups
Click on Add to create a new group
Give it a name and click Create
Add contacts to a group
Click on Contacts at the bottom left of your screen
In the menu that opens, click on Contacts or on a specific contact list
At the right of a row, click on Add to a group
Select the group you want to assign the contact to