Pointing Your Domain Name to Blogger
If you have your own custom domain, from a 3rd party registrar, you will need to login to your account with them and point your domain name to Blogger from there. In order to do this you will need to create a CNAME record for your blog's address. To create a CNAME record for your domain with the DNS, associate your domain with: ghs.google.com.
The exact procedure for doing this varies depending on your domain registrar, however Google does maintain instructions for some of the more common registrars. If your registrar is not listed you can e-mail the support department of your registrar and they will be able to give you instructions specific to your domain.
You will also want to create an 'A' NAME records for your naked domain (myblog.com). The reason to do this is to ensure that people who try to access your blog using myblog.com instead of www.myblog.com will still be directed to your Blogger blog. If you do not setup these 'A' NAME records anyone who tries to access your site via myblog.com will see an error page.
You can usually setup your 'A' Name records using the same interface you used to setup your CNAME record. The four (4) different IP addresses you need to use for 'A' Name records are: 220.127.116.11, 18.104.22.168, 22.214.171.124 and 126.96.36.199. Again, if you need help with any of these settings your domain name registrar will be able to help.
Source: Google Blogger Help