Click "Contacts"-->"Add friends"-->"Phone Contacts". Here you need to allow CAD Viewer to access your cell phone address book. Then the list of contacts in your cell phone address book will be displayed.
Select the contact you want to add as a friend from the contact list in the address book and click the "Add Friend" button to complete the add friend request. After the request is completed, you need to wait for the friend to verify before establishing a friendship. You can use other methods to notify the friend to download the latest CAD Viewer and pass your verification request.