OK, type your username and password in the login box:  John D  (dont forget any spaces and it's not case sensitive).

The login area will now say:

Welcome! Login.. 
Hi, John D
      
Who's Online?  
John D  <----------click here

This will take you to your profile page. At the top left of the profile page you will see a button: 'edit' <--------- click edit

You will now see this form:

Edit Your Details

Contact InfoName:    John Doe
User Name:   John D  
Email:     This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Password:    <--------------type in new password here
Verify Password:   <-------------and enter again here
User Editor:  
RA Membership No.:   
How did you hear about us?: 

Click 'update' to finish changing your password.