WhatsApp Business is a free to download app for small businesses.

Before downloading the app, please be aware of the following:

• If you have an existing WhatsApp Messenger account, you'll have the option to migrate your chat history to your new WhatsApp Business account. We recommend that you make a manual backup before proceeding.
• Your chat history can't be migrated back to WhatsApp Messenger if you decide to stop using WhatsApp Business.
• You can use both WhatsApp Business and WhatsApp Messenger. Each app, however, must be linked to its own unique phone number. It's not possible to have one phone number linked to both apps at the same time.
• The app is currently being rolled out to the world. If it's not available now, please check the App Store again later.

Then:

1. Download WhatsApp Business from the App Store
2. Verify your business phone number, the one you wish to use to talk to customers.
3. Restore your chat history, if you wish.
4. Set your business name.
5. Build your profile. Tap Settings > Business Settings > Profile.