Groups allow you to easily manage your address book and send out Bulk Messages or Group Messages to a subset of people. You can create a group from the contacts in your account; you can read more on how to do that here. 

You can also create new groups and add existing or new contacts to them any time!

Just click here, go to Contacts on the left-hand side → ‘Create Group’ on the top left.

Give your group a name and hit 'Create Group'.

After you have created your group it will show up below "all Contacts" or the last group you have previously created. After pressing  multiple options show up. You can send a campaign to the group, delete the group, export the contacts in the group, and edit any group with the icons on the right-hand side of your groups.