To secure your blog domain name registration first, register your domain name with a domain registrar (e.g., GoDaddy, Namecheap, or Google Domains) and check the availability of your blog name as a username on popular social media platforms. Depending on your blog's size and scope, you may also consider registering your blog name as a trademark for legal protection against others using your name or a confusingly similar name for similar products or services.