You can edit a Contact inside the Address Book as follows:
Step 1
Tap on the Settings icon from the bottom-right corner of the Portfolio. Then, tap on the Address book under Wallet section.
Step 2
Select the blockchain, go under CONTACTS, and tap on the desired contact to edit. Then, tap on the EDIT icon.
Step 3
Edit the Contact name as desired, then tap on EDIT button. Finally, enter the PIN code to confirm.