Sending SMS / MMS Messages

Hello.

How can I send the SMS and MMS messages via API?

Currently, I created clientId & clientSecret which I use to get access token. Now I want to use that account to send SMS & MMS messages via API from a specific phone number.

Let’s say I have a sender with the phone number +14541111111 and a recipient with phone number +14542222222. And I want to send SMS with text Hello and attachment Attachment.jpg to the recipient. What API endpoint or endpoints should I use?

How can I register a new phone number as the sender phone number?