1

Open the People tab in the Messenger app. You can sync your contacts with Messenger to add people from your contacts list that use Messenger to your Messenger friends list. Syncing contacts will also automatically update your Messenger friends list whenever you add a new contact to your device.

Contacts are only added if they've associated their phone number with a Messenger account.

2

Tap "Sync Contacts" at the top of the People tab. If you're using iOS, you'll need to tap "Find Phone Contacts" first. Messenger will scan your contacts and find people to add to your Messenger friends list.

If you're using an iOS device, tap the "Open Settings" when prompted. Toggle the "Contacts" slider 

on, then tap "Return to Messenger." Tap "Sync Contacts" again to perform the sync.

3

Tap "View" to review the contacts that are added. Messenger will display all of the contacts that it found Messenger profiles for. These people are automatically added to your Messenger friends list, so no action is required on your part.

If no contacts are found, Messenger will still continue to scan your contacts list for new contacts that may be using Messenger.

4

Turn off contact syncing to remove contacts added during the sync process. If you no longer want to sync contacts from your device's contacts list, you can disable contact syncing. This will delete the contacts that you've synced automatically:[1]

Open the Settings (iOS) or Profile (Android) tab in Messenger.

Select "People."

Toggle "Sync Contacts" off. Confirm that you want to delete the contacts that you've synced.