You will encounter the Address Book Picker in many places. Let's run through the basics.
This area will show you your current selected records.
You can use the plus button to add a new record. If a record has already been selected, you will have options to unselect it or edit it.
There are three components to the address book; Companies, Contacts, and Addresses.
You can search for records to speed things up.
Make you selection from the list.