You can start building with Twilio by watching this screencast on sending SMS messages, which provides a step-by-step guide on making a REST request to Twilio's API to send an outgoing SMS, and learn how to build your own Twilio app along with the tutorial "Sending SMS Messages". The screencast is part of a series of tutorials designed for new developers to accessibly build with Twilio. You can also find additional resources, including API reference documentation, SDKs, sample apps, and more, on the Twilio website.