Select Bulk Email from the Email drop-down
Enter all of the email addresses you would like to be in the group into the Additional Recipients box, using a ; to separate each address
After you have entered all of the desired email addresses, click Save This List
Enter the name of the group you wish to use
Click Save As New Group
After saving your custom group, you can find the group by select Custom Groups in the drop-down
Click the + next to your custom group to add it to your communication
Click the - to the right of your custom group to delete it
Click View/Remove Members to view or edit the group