Please login into your account and proceed to Settings. In Security Settings section you will see an option to create the API key for iOS app.
Press 'Create' and you should see a pop up window confirming that an email with further instructions has been sent to you.
Please proceed to your email and use the provided link to generate API key. Please note that the link is valid only for one hour.
In the next window you will see a pair of an API key and a secret key and a corresponding QR code.
Use Covesting iOS app to scan the QR code or enter the key pair manually. The iOS app will prompt you to set a PIN code. Once you've set the PIN, you can use it to login to the iOS app on your device.