[OS X TeX] fonts

[juan tolosa]

I want to add a Sans Serif font to a document. Looking at the "Fonts" and "Manage Fonts" tools, I found Gill Sans.
However, something naive, such as

\font\gm=Gill_Sans

(this is the way I have been introducing fonts in TeX so far, say \font\sc=cmcsc10 to use Small Capitals)

just did not work.

How can I use the wide set of fonts available in the ``Fonts'' list?

Thanks,
              Juan