To enable Cloudflare on a wildcard sub-domain, you need to first register a free Cloudflare account. Once you have a Cloudflare account, you'll need to update your domain's nameservers at your domain registrar to point to the nameservers provided by Cloudflare.

After your domain is active on Cloudflare, you can create a wildcard DNS record. This is done by adding a DNS record with an asterisk * in the "Name" field. Cloudflare will then provision a Universal SSL certificate for your domain and its first-level sub-domains, and you can enable proxying (the "orange cloud") for the wildcard record to apply Cloudflare's security and performance features to all traffic that matches it. This will only apply to sub-domains that don't have a specific DNS record of their own.