How do I create an API key?
Choose Create API key. Give it a Name, and under What it can do choose what the key may do. Confirm your email address first. If it is not confirmed, the screen says Confirm your email address to create an API key.
The next screen says Copy your API key now. This is the only time we show the whole key. Store it somewhere safe. If you lose it, revoke it and create a new one. Choose I saved it when you have stored it.
The key screen says the API terms are a draft, and that creating a key records the draft's version. Notice and terms says what that means.
The steps to send the first request are on the Quick start.