https://support.google.com/blogger/troubleshooter/1233381?rd=1

How do I use a custom domain name for my blog?

Blogger offers two publishing options for your blog: hosting on Blogspot (example.blogspot.com) and hosting on your own custom domain (www.example.com or foo.example.com). You can change your publishing option at anytime, and your content will always remain unaltered regardless of which of these options you choose.

Before you move your blog to a custom domain, you need to have already purchased a custom domain (www.example.com) from another provider, as you can no longer purchase custom domains through Blogger. There are many companies from whom you can buy domain names, usually for very reasonable yearly prices. A Google search for "domain registrar" will turn up numerous options. Here's a quick list:

• EasyDNS
• GoDaddy.com
• ix web hosting
• 1and1
• Yahoo! Small Business
• No-IP

If your content is in a different language and you'd like to purchase a country-specific domain, you can do a search for local registrars. For example, if your blog is in French and you'd like a www.example.fr domain, then you should look for "Domain registrar in France."