Your API key is referred to in Niteco Performance Insights as a PAT(Personal Access Token). In order to make API requests you must authenticate your requests by adding the API key as a header:
x-api-key: YOUR_API_KEY
Finding Your API Key
To find your API key click on the account menu in the top right of the page.

Click on User Information

Copy the Personal Access Token by clicking on the copy icon next to it.
Super Admin usage
Super Admin role has the ability to manage API Keys of all clients. Navigating to Clients and click edit icon for a client. You can see all client details along with their API Key.

To regenerate your API key, click on Regenerate API Key.