It may have been for an outdated version, but the major idea is that you can prevent computer illiterate people from taking images but anyone who knows a thing or two about computers know that disabling right click is useless. But it is a small step in securing your stuff.
You can open the header file (I think it is the header file, someone might know the exact name and where it is) - I don't remember exactly where this file is (if you are not familiar, go to view source from your browser and read the first line and find the file that has the exact first line excluding comments) file for zen cart and insert it before the <body> tag begins. If you are placing it within the <body> tags then it may not load up properly.
Also this may edit the internal files and you should only use the override system when doing this.