You’re Already Friends on Facebook
Facebook friends are automatically added to the Messenger app when you sign in to Messenger with your Facebook account login details. To start a conversation with a Facebook friend in Messenger:
You’re Not Facebook Friends, But They Use Messenger
If you’re not already friends on Facebook but you both use Messenger, exchange username links so you can communicate on Messenger. To send your username link:
They’re Stored in Your Device’s Contacts
Sync your mobile contacts with Messenger to communicate with them in the app. To do this, turn on Contact Uploading in Messenger.
You Know Their Phone Number
If you prefer not to sync your contacts with Messenger, or you have someone’s phone number written down, but they are not stored in your device’s contacts, add them to Messenger with their phone number.
Meet Up in Person
If you’re with someone and you want to add each other on Messenger, use any of the above options or take advantage of Messenger’s user code feature (Messenger’s version of a QR code), which makes adding people in person quick and painless.
