Create a file analyticslink.config and put it at /Data/Sites/[SiteID]/supplementaladminmenulinks/
the contents of the file should be:
<?xml version="1.0" encoding="utf-8" ?>
See also Adding Custom Items to the Admin Menu.
Note that the In Site Analytics Pro product has been discontinued quite a while ago, is no longer on sale and technically is no longer supported. As far as I know it should still work but at some point I expect google will discontinue the API it uses which is why we discontinued it. At that point it will stop working but as far as I know they have not done that yet. We only sold 7 copies of it and it would be a huge amount of work to re-write it using their newer APIs.
Hope that helps,