When you first start up Geocache Navigator it will ask for your phone number and PIN. The PIN is a unique numeric value that is known and created by you. The purpose of the PIN is to allow you to connect your phone to an account on Geocaching.com. The account on Geocaching.com provides you the ability to add detail about your finds and share your experiences with the rest of the geocaching community.
For more information on connecting to geocaching.com, click the "Get Started 'menu option on the geocachenavigator.com web site and select "Access cache logs"