If you have already created groups within the Contacts section, there may be times where you'll need to add a new contact to one of those groups. For example, if a new team member comes on board or those from another department get added to specific regular meetings, you'll want to add them to the appropriate contact groups.
Here's how you add contacts to your contact groups.
Open your Calendar account and select "Contacts" from the menu that appears on the left side of the screen as shown below.
Click on "My Contacts" and select the person you want to add to a Contact Group.
Select the contact or contacts you want by ticking the box next to their name as the picture above illustrates. Next, choose the Contact Group you want to add them to.
Click "Apply" and then that contact will be added to the group as shown below.