First you have to buy a domain name ,they are many webs which provide domains , if you have domain name then login into your Blogger account and then follow these below steps as show in the image
Once you have finished these steps just login into your domain panel and follow these steps
here is google tutorial if you are not able to understand this you can comments us, feel free to contact us
or here is a video tutorials for DNS record
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it will be nice if you post the dns settings for cpanel