Click on the Get a trial phone number and copy the phone number that you will enter in your General Settings as Sender phone number.
ClickSend is a global leader in business communication solutions, their reputation is built on technical expertise, industry experience, quality support and service reliability. From bulk marketing to mission-critical solutions
ClickSend lets you send SMS messages globally, through A Web Based SMS Portal or Transactional SMS via SMS Gateway API. Using ClickSend SMS you can be confident your customers and staff are receiving and reading your SMS messages.
How to get your ClickSend API Key:
Login into your ClickSend account.
Navigate to Developers > API Credentials
You will need to enter Username & API key in your General Settings.
Copy the API Key and use it in the SMS provider settings.