Lightbox Plus Question

Any help will be appreciated. I have downloaded Lightbox Plus and it works fine if I use a default theme, but I have a custom theme and it will not work.

Does anyone know if I need some kind of special code in my theme that will allow this type of plug-in to work properly? I tried comparing the code between the two themes, but I really don’t know what to look for.

Any help will be great. Thank you.