Once you have added external sources to your iOS device, you can sync the data from the 'Contacts' application with Mapview.
1. Start by opening the main menu and choosing 'Settings'
2. Scroll down to 'Choose groups to sync'
3. Choose the groups you would like to import
4. Tap 'Done'
*Groups from Gmail do not sync and will be under one group entitled 'Gmail' in an iCloud section.