How To Use Namecheap Domain With Blogger Account

In order to use namecheap domain with blogger account, you must do several following steps:

Login to your Blogger account, then click on Settings tab and choose Basic, click on Add a custom domain button under Blog Address field in Publishing section. When this is done, you'll see a field to put your domain name in.
Input the domain name and click Save button. after the page refreshes, you will see two CNAME records which should be created in your domain’s Zone File.

Login to your namecheap account, then click on Manage domains on the drop-down menu. Go to All Host Records in the left-hand menu, and create two records for your domain.
 

For your @ field you put http://www.yourdomainname.tld (make sure you put your domain name and do not forget  about the http://www. part) and choose URL Redirect as a record type from the drop-down menu. For the www field you put ghs.google.com and choose CNAME as a record type from the drop-down menu.

Enter the value listed under Name, Label, or Host field in "Host Name" field, verification string (xxxxxxxxxxxxx.domainverify.googlehosted.com.) listed under Destination, Target, or Points To field in "IP Address/URL" field and select CNAME from the "Record type" drop-down menu under "Subdomains Settings ". 
Finally, click on Save Changes button at the page bottom.