To begin sending RCS messages to your customers' mobile devices, you need to register and launch a sender using the Provisioning API. This means submitting sender business and branding details, as well as completing a launch questionnaire about the purpose and the content of the messages. You can also specify test phone numbers to preview the appearance and functionality of your messages on a RCS capable device.
Check the RCS senders guide to learn more.
Note:
You may also go to the Sinch Build Dashboard to view and create RCS senders via a user interface.