You can change your password and most other settings and information by logging in and clicking on your User ID in the upper tool bar near the top of the screen. Password is under Password and Security. Other account settings are under other tabs that will appear after clicking on your User ID. However, to change your User ID, you will need to send a PM to one of the Admins and request that they change it. I am not certain whether need your password or not. But as you are going to change it anyway, go ahead and include it in your PM.
I would recommend that you get your User ID changed first. Then change your password.