Back To Top for Blogger

Log in to your Blogger account
Click to "Design">"Page Element"
"Add a Gadget" and paste this code then Save.

<a style="display:scroll;position:fixed;bottom:5px;right:5px;" href="#" title="Back to Top"><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj20y0-iJfa3KftWDHQCMvKFGA2IOXR3gP6diGDZI-K1vchw3mPPrYsZ6wwCx15a6nII6bgW5cb752gy7VHmTwmGKsZWQRohna2TvYFPIXLq152NGfTBQ6uoIjpctIYnIVVn2XxUP9ts1Ne/s1600/arrowupcx2.gif" /></a>

You can change any icon you want to use to appear on your blog, 
Just change the Link in Red color.