hello and welcome!
mapping for oa is more or less the same as mapping for quake 3 - which gives you a lot of tutorials all over the interweb!
there might be other mapping tools out there, but most of us use
gtkradiant 1.5.0openarena is not supported in gtkradiant from the beginning - you have to copy and edit some files first.
here's a short guide on steps to take:
DO NOT LINK[/b]) h t t p s : / / openarena . wikia . com/wiki/Configure_GTK_under_windows]configure gtk under windowshere's a wikibook for gtkradiant that i found now when i wrote this reply:
gtkradiant - wikibookgood luck