Are there instructions for configuring the subscribe-single-fixed.php page? How do I choose the list it's subscribing to. Where do I put this file? Do I just keep it in the html folder that it's already in? Should I copy it and rename it?
Those are sample files. The ones with the 'auto' word in their title work automatically, with the others you have to tell the list name. The 'subscribe-single-fixed.php' is not automatic so you have to add the list name as a parameter like this:
You can put the file wherever you want and even rename it.