You can add a new email address to an existing address book by either adding the address manually or by importing addresses from an Excel or CSV file.
Importing addresses is a good option when you have several addresses to add.
Add a new contact manually
Select Contacts from the navigation bar in order to display your address books. Tick an address book and then click on the Add contacts icon alongside it.
You will be asked how you want to add your contacts. Select Add an individual contact.
You are then prompted to add the email address for the new contact:
When ready, click on Continue.
You can then complete additional information about this particular contact. When ready, click on the Save button to complete adding your new contact to the address book.