Log in to your computer with your old password or your temp one given to you by IT or your supervisor/manager.
Step 1: Once you see your desktop, press ctrl + alt + delete on your keyboard
Step 2: Choose Change a password

Step 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.