Following its username feature rollout, WhatsApp is now letting users save a contact's username when they add their name and phone number. The username field is shown between the first and last name fields and the phone number section.

You can add a new contact in WhatsApp by tapping the + button in the navigation bar of the Chats tab. According to WABetaInfo, when usernames become more widely available, WhatsApp will populate the username field automatically when users create a new contact from the chat info screen.