Endnote Web - adding a journal style


I use Endnote Web and have a plug-in for using WORD on my Mac. I’m writing a paper and want to set a bibliographic style for a specific journal. However there only seem to be about 21 bibliographic styles that come as standard on the Endnote Web site - these are also the same ones available via my plug-in.

I haven’t been able to work out how I add an additional bibliographic style. Can I do this using Endnote Web? I feel as though I’m missing somethng obvious - I’m sure it must be possible , and I see there is a plug-in for the journal style I’m interested in, but when I download that onto my hard drive It doesn’t seem to make a difference.

Any advice very gratefully received.