Simple sign up and text account creation. https://www.clickatell.com/
Choose “Create an SMS integration to use in your own application” and follow their instructions.
Set up a test phone number.
Create a test API (They ask for billing details to send a test message but not for any credit card information, just name and address is enough to activate their API.)
Copy the API key to our Settings in WP-HR SMS, add username and PW and you should be set to go.