With the Broadcast List feature you can send a message to several of your friends at once.
Broadcast Lists are saved lists of message recipients that you can repeatedly send broadcast messages to, without having to select them each time.
To create a Broadcast List:
To send a broadcast message simply tap the Broadcast List that you created > Type the message > Tap Send.
Note: Only contacts who have added you to their phone contacts list will receive your broadcast message. If your contact is not getting your broadcasts, check to make sure they have added you to their contacts.
To edit a Broadcast List:
WhatsApp Support Team