Open Policy Manager to set Terminal Server timeouts

• Open Command Prompt
• Run mmc.exe
• Mmc
• File > Add/Remove Snap-in
• In Add/Remove Snap-in dialog box, click on Add button
• On next dialog box Choose Group Policy Object Editor. Click Add.
• Accept Local Computer by choosing Finish.
• Close everything.

 For Terminal Server try:

Local Computer Policy > User Configuration > Administrative Templates > Windows Components > Terminal Services > Sessions

Or

Local Computer Policy > Computer Configuration > Administrative Templates > Windows Components > Terminal Services > Sessions