Alternatively you can use anchor links....simply go to Settings >> Advanced >> Code Injection. Then in the header section add the following code:
<div id="ScrollUp"></div>
This simply labels the header div as "ScrollUp" so you can just refer to it using anchor links.
Now go to your footer, and either add a button or just a text that says something like "Go to top". Then in the links section of either the button or just a hyperlink on the text (if that's what you used) then put the following in that links part:
#ScrollUP
Save and try it out! Should work. Let me know if any questions regarding this.
Cheers!