Windows 8 have .Net Framework 4 and above pre-installed. But we need .Net Framework 3.5 for running several old applications. So better to install it.
Installing from Windows 8 DVD/PD
1. Insert your Win8 DVD or Pen Drive
2. Run the following command as it is in elevated Command Prompt. Type it or copy-paste from below-
dism.exe /online /enable-feature /featurename:NetFX3 /Source:G:\sources\sxs /LimitAccess
Note: the above command is case sensitive
Replace :G: to your windows DVD or PD's drive letter
Installing from Windows 8 DVD/PD
1. Insert your Win8 DVD or Pen Drive
2. Run the following command as it is in elevated Command Prompt. Type it or copy-paste from below-
dism.exe /online /enable-feature /featurename:NetFX3 /Source:G:\sources\sxs /LimitAccess
Note: the above command is case sensitive
Replace :G: to your windows DVD or PD's drive letter