You can invite your friends to Wickr Me by going to your Settings > Contacts > Tapping + Invite Contacts.
You can then invite your friends by either sending a text or email from your device providing your soon-to-be contact with your Wickr ID and pointing them to the App stores so they can download the app. They will need to download the app, and create a Wickr ID to communicate with you on the App.
We never store your device contacts on our servers. All invitations are generated locally on your device, without sharing any information with us.