Here are the simple steps to follow if you want to point the domain you purchased from Namecheap to your Blogger's blog.
1. Log-in to you Blogger account and then go to Settings -> Basic and click Set-up a 3rd Party URL for your blog.
2. Type the domain that you just purchased from Namecheap. Make sure to add "www" and then click Save.
An error message will appear stating that they have not verified the authority of the domain. Don't worry because you can set this up in your Namecheap account. Just take note of the CNAMEs provided because you will need these details.