In order to link your domain to your blog, you need to take several simple steps:
1. Set up your domain in your Blogger account.
Sign in to Blogger
Select the blog to update.



Click on the Settings tab and choose Basic
In the Publishing section, click on the link'+ Set up a third-party URL for your blog' to add a custom domain:

Type the URL of your domain , ensure it starts with www (or any subdomain) in order to work. Input the domain name and click on the Save button:

Note: Blogs are not to be placed on empty domains (like mydomain.com) , so you need to input a subdomain, for example, www.mydomain.com or blog.mydomain.com.
Once the page refreshes, you will see two CNAME records which should be created in your domain’s Host records:

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 unique to your blog and your Google Account, and is therefore different for each person.
2. Create the necessary records for your domain in your Garanntor account.
Sign into your Garanntor account.
Click on Domains :

Click the drop-down arrow beside the domain and from the drop-down list click on DNS Manager:

Add a New DNS Record and save:
NOTE: You will need to create 6 records for your domain:
- (Four) A Records for @ pointing to 216.239.32.21, 216.239.34.21, 216.239.36.21 and 216.239.38.21
- CNAME for www mapped to ghs.google.com
- CNAME with values provided in the Blogger account

Save all the DNS Records created :
s
After your settings have been updated, you need to make sure Blogger knows about your custom domain so that Google can direct readers to your blog.
Login to your Blogger account and save the information on your Basic tab:

Source:https://www.9jagossipers.com.ng/2019/07/how-do-i-use-my-domain-with-my-blogger.html