jed -> gnus newbie

[notbob <notbob@nothome.com>]

I've got gnus running, have my nntp server variable set, but still
can't post.  When trying to post to a test ng, I get an error msg:

Denied posting -- the From looks strange: "notbob@xxxx"

.....xxxx being my Slack box'es host name.  OK, I'll change it to
whatever.com, but where do I set the "from" header variable?  Also,
what about the other header settings like "name" (nick),
"organization", etc.  I've been run ragged looking for info in my
Learning Gnu Emacs (O'Reilly, 2nd ed) and emacs and gnus online
manuals.  But, info on these settings and others like my pop3 and smtp
server settings are still unfound by me.  My.gnus.org talks about M-x
customize (ret) mail (ret) as being the way to do it.  I'm running
emacs-21.3-no-x11 on a Slack 10.1 Konsole and these commands do
nothing, me getting no mini-buffer prompt after "customize (ret)" and
no "mail" category in the customization or lower buffers.  Usually, I
can work this stuff out, but now I'm feelin' dumber'n a bag o' hammers
and my eyeballs are down to their last good nerve.  Can anyone help?  

TIA

nb