Sheep has an API (Application Program Interface) - a way for other computer systems to securely talk to Sheep. An API key is like your password, guard it and choose who you share it with carefully.
For improved security and audibility create a separate user account for each API key
Creating an API key
Navigate to settings
Select your user profile (Person icon with a spanner on the blue left hand menu)
Click on the 'Additional Details' card
Choose your API key (like your password it should be suitably long and complex)