[Users] Claws Mail themes directory

[edwardp at openmailbox.org]

(Looks like my original e-mail didn't make it to the list. My apologies
if it eventually makes it.)

I'd like to install the Claws Mail themes file on Linux (Fedora 22,
64-bit), but this is the first I've seen a reference to $PREFIX, I'm
just an end user, not a programmer.  :)

Does $PREFIX represent a specific directory?

Thank you in advance.