editing pg_hba.conf

hello,

i have installed postgresql, and it's up and running fine, using the
postgres user account.  however, when i run the pgadmin III utility,
and attempt to File>Open pg_hba.conf file, i cannot select it from
it's /data folder because it is obviously locked.  i am using my
default os x user account, and so i clearly to not have access to that
postgres user folder.  although i have a postgres user account, i do
not have a postgres user account listed under my Preferences >
Accounts.  should i create one here?  or is there any way to make the
existing postgres account visible in my Accounts list?

so, the question is; what would i need to do in order to make that
file easily selectable/editable using the pgadmin III utility
File>Open pg_hba.conf?  whilst remaining logged in using my default os
x user account?

i would prefer being able to use pgadmin to edit this file, instead of
having to use Terminal > sudo su > su -l postgres > vi/emacs
pg_hba.conf.  also, i have not had much success in using vi or emacs
to edit the file, because it is read only, and i haven't been able to
figure out how to overcome that(i've shut down the postgresql server).

thus, any advice would be greatly appreciated.

thanks,

eric jarvies