Create a personal mail group with Directory Information in Google Contacts

Watch How to Create a Personal Mail Group with Directory Information in Google Contacts:

To add a contact to a contact group from the Directory:

1. Select the Directory label.
2. Search the Directory for the contact.
3. Select the contact in the Contacts list.
4. Click the Groups button. 
5. Select the group you'd like to add the contact to, or select Create new to create a new group.

Reference: Google Groups Help - Editing Contacts