First, sign up for an account. To get started with testing, obtain a free sandbox number by navigating to Development > Sandbox numbers in the left sidebar.
You can purchase production numbers later when you’re ready to go live
Click Get number and enter a phone number to whitelist—for security purposes, sandbox numbers can only send messages to whitelisted numbers. After clicking Get number, you’ll see a card displaying your new sandbox number. Click the phone icon on the right side of the card, then select the smartphone icon and enter the 4-digit PIN that was texted to your device. Once verified, you can copy your sandbox number by hovering over it on the card.
Navigate to Development > API Keys and click Create API Key. Give your key a descriptive name, then click Create. Once generated, copy your new API key and store it securely.