To enable access from iPhone users, you'll need to create a user group made up of people who'll be using the iPhone application, then grant iPhone access permissions to that user group. For more on user groups, see Managing User Groups.
Admin Console: System > Settings > Mobile
The iPhone Management page lists all of the iPhone devices that have connected to the application, along with the user's username and the time they last logged in. To prevent a device from accessing the community, select its disable check box.