In order to authenticate your domain, first you need to create a CloudFlare account.
There are 2 ways to connect your control panel to your CloudFlare account:
1. Using your CloudFlare email address and API Key. A guide on how to obtain your API Key can be found here - developers.cloudflare.com/api/keys/.
2. Using an API Token, you can follow this guide on how to obtain a CloudFlare API Token - developers.cloudflare.com/api/tokens/create/.
If you would like for us to help you connect your control panel to your CloudFlare account you can create a hosting support ticket at the link below.