Here are the instructions

1. Make sure you have purchased enough RingEX licenses for your account. You must purchased using the RingCentral admin portal. This cannot be done via API!
2. Make sure that you have purchased also phone numbers and add them to your account inventory.
3. Create a user extension using this API
4. If you intend to assign a BYOD device or the RC app to the new user, add a device to the newly created user extension using this API.
   1. You will need to set the device type “OtherPhone” for BYOD or “WebRTC” for the RC app
   2. You will need to set the emergency location. Read the emergency locations and get the id using this API.
   3. You will need to set the phone number (in the inventory) using the phoneNumberId. Check the inventory number and get the phoneNumberId using this API (usageType=”Inventory”)
5. If you intend to assign an existing device (provided that you have purchased a device using the admin portal), then use this API to update the device by assigning it to the new user extension.

Alternatively, you can use the SCIM API to create a user and the system will choose a device and assign to the user.

Hope this helps.

Very helpful, thank you!