To send a card enter the Email Address or Username of the recipient.  Optionally, you can use the Advanced Options to capture the recipient's First Name and Last Name, add a Personal Message that will be sent with your card, and draft a Private Note you'd like to keep for this contact. 

In v3, when you send your card, the recipient's contact info and the Private Note you entered into the Send Card screen is automatically added to your Contacts list.