Well, I've read through a few of these posts and see that this mod works with Zen Cart v1.3.7. I've included lines from this mod in my index.php (i think index file)
because it was already moded. I've put all the other files in and the sidebox file shows up in my Sidebox Layout menu. However, I have activated it and set it to the left column. The subscription box does not show up.

Has anyone else experienced this? If so how did you fix it. Thanks :-)