API Key creation is limited to project admins and owners. In your project's API section, you'll find a link to the API Keys page.
If you haven't created any API keys yet you'll see an empty list. Click the "New API Key" button
The API key has been created. Make sure you copy the key from this dialog and save it someplace safe and secure. This is the only time you'll be able to see or copy the API key.
Your key is now ready to use. You can delete the key if it becomes compromised or you no longer need it.