From a Home screen, navigate: Apps icon > Contacts.
From the Contacts tab, tap the contact.
Tap EDIT (located in the upper-right).
Enter or edit any of following information then tap SAVE (located in the upper-right). Depending upon the account type, the options presented may vary.
Name
Phone
Email
Groups
More (Phonetic name, Organization, IM, Address, etc.) To add more fields:
Tap ADD ANOTHER FIELD (located at the bottom of Edit contact screen).
Select applicable fields from the list. Selected when a check mark is present.