Have read (carefully, I hope) the earlier question Font installation in TeXShop on a Mac looked to be exactly what I needed. Also looked at http://www.tug.org/fonts/fontinstall.html#fndb
Am trying to install Arial from CTAN.
However, the sudo commands getnonfreefonts, texhash and updmap did not seem to be available on my system. So I have downloaded and installed MacTeX 2012 (previously had 2010), which enabled texhash and updmap, but not getnonfreefonts, and tried again.
The unzipped files went into /usr/local/texlive/2012/../texmf-local/arial which I think is right.
sudo texhash made all the right noises, as in the answer to the earlier question referred to above.
sudo updmap-sys --enable Map=ua1.map produced a limited response. I had made earlier attempts, sometimes with the wrong map name. The font is not 'working'. testfont confirms this, saying that ua1b8a (one of the .tfm files) cannot be found.
I have clearly 'screwed up' my system somewhere along the line, unless I have misunderstood something. What do I do now? Remove all traces of TeX... from my computer and start again? Or...
Sorry to be so dumb.