Syncing or downloading of Checklists and ITP Plan Items to your mobile device is automatic, which means you don't need to manually sync these items in the Manage Sync Items screen.
Just login to FTQ360 when you have Internet or cell service, wait for the "Loading Data" bar to complete and you can begin working offline. That data has been shared with your device.
Existing inspection and test reports will not automatically be synced/downloaded to your device. If you want to work on existing inspection and test report, you must go to the Manage Sync Items screen
For information, checkout Sync Inspections to Your Mobile Device.