Help wanted: Change password an username

I am doing some work with an Informix database. I am a total newbie on Informix and here is my problem: I need to insert some usernames/passwords for accessing my database. I mailed this to the database administrator, to which he replied "I now have made you DBA over your databases 'testdatabase'" and went on vacation. I don't have a clue how to insert my usernames/passwords, and there is noone to ask here. I now there is a program called "dbaccess", but it don't seem like I manage any of these things with that. I am using Informix 7.24 on a SunOs 5.5.1 machine. Can anyone help me with this? regards / Fredrik Fyring