
So to add a subscribe button to blogger blog, you need to find a big, beautiful RSS icon. Download it and upload it to your image hosting services and get the URL.
Next add a HTML/JavaScript widget and paste the following codes into it and save it. You can also write something into the widget to tell your readers to subscribe and then paste the following codes:
Now let’s have an explanation:
Change the feed address with your feed URL. Generally your post feed URL will be “http://your-blog.blogspot.com/feeds/posts/default”, but if your feeds are redirected to Feedburner.com, then it will be your feedburner URL as "http://feeds.feedburner.com/your-blog". Some of you may also want to add comment RSS, it’s URL will be “http://your-blog.blogspot.com/feeds/comments/default”.
If you want to change the image then find: src="http://lh3.ggpht.com/_dzq0x75P67s/S-eNuEhHhAI/AAAAAAAABfo/pxusYgKjxu4/s800/feed-icon-orange-48.png" and change the URL within the quotes with your hosted image.