Sign up to the Shotstack service to generate API keys. Keys for both a staging sandbox and a live production environment are available in the dashboard.
Find your keys in the menu under your account name (top right hand corner):
Click on the API Keys item in the menu to open the keys page:
Keys are a random 40 character string that look something like:
Staging sandbox and production URL's are:
|Sandbox URL||Production URL|
You can use your sandbox account as much as you like, rate limits apply and videos are watermarked.
Using your production key will use up your credits and may result in being charged.