Log into your computer with your old password or your temp one giving to you by IT or your supervisor/manager.
1) Once you see your desktop, press ctrl + alt + delete on your keyboard
2) Chose Change a password
3) You will be prompted to enter your old password or the Temp one given to you and then a new one.
***NOTE*** You can not use any part of your old password from the last 5 that you have used.