Enable .NET Framework 3.5 by using Control Panel and Windows Update (Windows 8 only)
For an installation of Windows 8 that has an Internet connection, the easiest way to add .NET Framework 3.5 is to download the required files by using Control Panel and Windows Update.
Access to Windows Update. If the PC or server is behind a firewall or uses a proxy server, see KB900935 - How the Windows Update client determines which proxy server to use to connect to the Windows Update Web site.
Administrator rights. The current user must be a member of the local Administrators group to add or remove Windows features.
On the Start Screen type turn on windows features, select Settings in the Search pane, and click on Turn Windows features on or off.
The wizard will search for required files and then prompt you to download the files through Windows Update.
In Windows Update, select Download Files.
After the wizard completes, click Finish.