
So first, you need is a Google Feedburner account by registering with them.
Now login and go to the “Publicize” tab:
Select “Email Subscriptions”. Within “Subscription Management” tab, copy the code that they will provide.

Now add a HTML/JavaScript widget, paste the code and save it. It’s done. If you are new then how to add widgets to blogger can help you.
Now comes the customization part.
If you want to remove the borders surrounding the email subscription box, then find for the bold codes and delete it:
Change the width to 150px or more, whichever suits you.
Now save everything and view your blog to see that if you have correctly added the email subscription box.