mozilla mail signature

[betty i]

this should be an easy question and since it is not too important, i've 
put off dealing with it til the hot weather when i'm indoors more and 
send more email.  
i'm using rh 7.3 and mozilla mail. i use the gui for almost everything. :-[
when i try to add my signature line in the
 'mail and newsgroups account settings'  it won't attach it to the mail.
  i've tried both - writing the line into the box next to 'attach this 
signature'
 and also - making the signature a document file and putting the pathway 
to that file into the box. neither one worked.

any ideas?
thanks betty i.