Click on My Profile in the right-hand menu of your home page (you should be taken to your home page as soon as you log in, if you need to get back to it, click Growth Zone or Member's Zone in the menu bar towards the top right of any page)
Click Edit my account details
Enter your new password in both the Password and Confirm password boxes
Click Save changes
You will see a yellow box with the message 'The changes have been saved' which means your new password has been changed successfully.