Best is to start by reading User Account Settings post and create new account for your kid.
Please read that post first and than proceed to the next step of creating Parental Controls.
When you are ready go to Start-Control Panel-User Account Family and Safety-Parental Controls.
Have your administrator account protected with strong password to prevent users to bypass and turn of parental settings and use the computer without restrictions.
- Set Specific time Limits to your children's computer use with different logon hours for every day. For example you can set your child computer use Monday to Friday limited to one hour because of school and let them play more hours on Saturday and Sunday.Under Parental control click On, Enforce current settings - Time Limits and than choose hours as you want to block or allow.
- Prevent from running specific programs. In case you are using some programs that you want prevent other users, your child to access than click on Allow and Block specific programs , switch to "User Account can only use the programs I allow" and than choose programs from the list. Also there is an option where you can add the program to the list in case its not shown.
- Prevent your Children from playing specific games. You can Block All Games or Block Games by age rating, by content or you can block specific games. Go to Parental Controls - User Controls - Game Controls and decide whether User can play all games or have restrictions to some games.