Running postgresql problem??

I have a problem running postgresql, refers to the postgresql user. Say X
has created postgresql user "postgresX", is a member of the group "class",
I am also a member of the group "class" ,have rwx permissions on the group
"class", and my user account is "user2". I am unable to run the postgresql
that X has created. How do I run X's postgresql , by using my login user2?

also, if X has created a postgresql user "postgreX", change he change this
user to that I can also have the same access to postgres that he has
installed?
Specifically, this is the error that Iget:

csil-sunb23|/usr/dcs/csil-projects/cs411/cs411g3/postgres/bin|[142]% postmaster
-B 32 -N 16 -D /usr/dcs/csil-projects/cs411/cs411g3/postgres/data
>FATAL 1: configuration file `postgresql.conf' has wrong permissions
>
>cs411ta2|csil-sunb23|/usr/dcs/csil-projects/cs411/cs411g3/postgres/bin|[143]%
>

I am logged in as "cs411ta2" to run postgresql created by "cs411g3". I am
a have the rwx permissions on the group "ta411" that both "cs411ta2" and
"cs411g3" belong to.

thanks