Adding an RSS Feed to your blogger/blogspot

Log in to google feed. ( with your google account)
Create a Blogger feed. (help) .
After creating the Blogger feed Go to "Publicize" Tab and click "Chicklet Chosser" link"

Select "Subscribe in a reader" radio button , select "Blogger" in "Use as a widget in" dropdown box. And click on Go button. Will navigate to below page.

Choose Title, will show in your blog. And press on "Add Widget" button. Will add the widget to your blog.

You can choose the widget location in layout page and save arrangements. 

Go to your blog and will able to see the RSS Feed button in your blog.