Defining 'C' functions in Postgres

Hello
I am using Postgres for the first time. I tried to define a 'C' function
in Postgres using the CREATE FUNCTION command but encountered the
following:

ERROR: Only users with Postgres superuser privilege are permitted to
create a function in the 'C' language. Others may use the 'sql' language
or the created procedural languages.

The command is
CREATE FUNCTION phone_in(opaque)
RETURNS phone
AS '/home/M97/acs/vassilik/protein/phone.o'
LANGUAGE 'c';

It is not me that installed Postgres. Is this the problem?

Kostas Vassiliadis