Floating Text Box with Links

It was mentioned previously here in one of my posts that a floating Back to Top button would be preferable to a single link at the bottom of the page or as I was intending having a number of links at specific intervals of the page.

I have looked into this and would like to implement this in my site. I want to add a message box with a link plus a Back to Top button box that floats up and down the page as the visitor does so.

Can anyone suggest a way I could do this please?

Thanks in advance!