How to map domain to Blogspot
Go to your blog and click on Basics under the Settings tab. In the "Publishing" section, click the link to add a custom domain.
Add a custom domain
Type the url of the domain you've purchased, keeping in mind that it must begin with www in order to work.
You should see an error, and two CNAMEs listed below. Each CNAME is composed of two parts - Name, Label or Host and Destination, Target or Points to.
The first CNAME is the same for everyone, Name being "www" and Destination "ghs.google.com." The second CNAME is particular to your blog and your Google Account, and is therefore different for each person.
After that, you can now login to your client area >> Domains >> My domains
click on the small arrow beside the domain >>DNS manager and add your CNAMES
NOTE: you will have to allow 3 - 72 hours for it to propagate
BLOGSPOT >>>HOW TO REDIRECT NON-WWW TO WWW
Go to Blog's Basic Settings and under publishing tab > Click on edit and Tick the checkbox that says "Redirect mydomain.com to www.mydomain.com"