alright, we'll use vi:
vi /etc/proftpd.conf
# use arrow keys to scroll into the <Global> section.
# press 'i' to enter the "insert" mode, and type
AllowForeignAddress on
# to give you the following:
<Global>
AllowForeignAddress on
DeferWelcome on
RequireValidShell no
DefaultRoot ~
....
# press ctrl-c to escape "insert" mode, then press shift-Z twice to save and quit.
service proftpd restart
# to restart proftpd.
John