If you’ve forgotten your password, it can be reset by clicking here or accessing the “Forgot your password?” link via the sign in page. Enter your account’s email address into the relevant field and click on the “Send me reset password instructions” button. Then follow the instructions in the reset password email.
To just change your password, go to your user profile page and enter a new password into the field and re-enter it into the password confirmation box. Next enter your current password into the current password field and click save. Note that your password can also be changed by following the reset instructions above.