You can make an API key in "Settings" > "API keys".
Click on the large orange "+" button on the bottom right of the screen to create an API key.
There's also a link to the docs on the top right of the screen. Here's a direct link to the docs.
The authentication is bearer token authentication, which means you need to use the key-value pair "Authorization : Bearer APIKEY" in the header to authenticate.
In case of further questions on the topic, reach out to use on the live chat.