Open Local Users and Groups: Either go to Computer Management\System Tools\Local Users and  choose Groups\Users or run lusrmgr.msc from the command line.

•In the console tree right click on Users

•Right click the user you want to add into a group, and then click Properties (figure 1:1)

•Go to the Member of tab (figure 1:2)

•Click on Add (figure 1:3), and then type the name of the user group e.g. Performance Monitor Users .(figure 1:4)

•Click OK, and then click OK again.

Figure 1: Adding a local user to a local user group in Windows 2008 R2