If you'd like to change your password, you can do so at any time. Simply:
Head to your "Account settings"
Click 'Edit your personal details'
Select “Change password”
Click the “Send me a link” button
Select the “Reset my password” button in the email sent to you
Type in a new password in the text box and select “Save new password”
Your password has now been changed, and you will receive an email confirming your change.