If you wish to change your password, you should go to the options screen, by clicking on the options button on the top of the screen. Then click on the change password button to open the following screen:
Type in your current password (your old password), the new password you want (your new password), and the new password a second time for confirmation (your new password again). The passwords you type in will be hidden, and should be shown on the screen as a set of asterisks.
When you have finished filling in the input boxes, click on the update button to confirm the change in your password.
If you cannot remember your password, your system administrator will be able to reset it for you.