Follow these steps to add contacts to an existing Group in your address book:
1. In the navigation, go to My Account > Address Book
2. Import or manually add your new contacts (hint: assign them all to the same 'category' to easily find them and add them later)
3. Click the "Groups" tab
4. Click the 'Edit' button next to the Group you want to add people to
5. Use the "Show" menu to filter the people displaying in your address book, to show the people you wan to add. If you entered the new people into your address book using a unique Category (mentioned above) then you can sort by that category.
6. Click the checkboxes next to the people you wan to add to the Group. (You can use the "Select All" checkbox at the top to check everyone on the page.)
7. Click "Save Changes" to update the Group.