Summarize this article:

Thereafter click Add and then choose Finish.

Summary:
Click the Start button from the taskbar. From the popup menu choose Run and in the dialog box that appears, type mmc and press the enter key or click OK. Click File from the menu bar and in the drop down list choose Add or Remove Snap-in and choose Add. Look for the tab labeled Available Stand-alone Snap-ins and click on Group Policy Object Editor.