If your password has expired before your next logon, you will be prompted to change this upon logging in.
To change your logon password while currently logged in.This can be done by pressing the Ctrl-Alt-Del buttons together. You will be prompted with the following screen, select Change a password
Ensuring all the fields are filled out, this should then change your logon password. (Passwords would need to have 8 characters, a capital letter, number and cannot contain your name or surname).