How to install or change user pass-word for computer?

I am a novice in computer operations. I have installed a home computer. My children are using it indiscriminately for video games. I want to install a pass-word for user of the computer so as to block access to my children.How to install or change user pass-word for computer?Click on START/SETTINGS/CONTROL PANEL/USERS ACCOUNT/ CLICK ON YOUR USERNAME and then click create password. Set yourself a secret question and answer in case you would forget your passwordHow to install or change user pass-word for computer?You go into the COntrol pannel then User Profile then click on your Account and add Password. Be aware that in XP home there is a Back door for that Password