To add a custom domain to your Blogspot blog, follow these steps:
First, you need to purchase a domain name from a domain registrar like GoDaddy, Namecheap, or Google Domains.
Once you have purchased the domain, sign in to your Blogspot account and click on the "Settings" button next to the blog you want to set up with a custom domain.
Under the "Publishing" section, click on "Set up a third-party URL for your blog."
Enter your custom domain name in the field provided, and click "Save."
You will now see instructions on how to verify ownership of your domain and configure your DNS settings. Follow the instructions carefully and make sure to add the required DNS records to your domain registrar.
Once you have verified your domain ownership and configured your DNS settings, click on the "Save" button in Blogspot to complete the process.
It may take some time for your custom domain to start working, so be patient and check back in a few hours to ensure that everything is working as expected.