Step by Step procedures in Activating .net framework 3.5.
Step1:
Search for Programs and features and click on
Step 2:
You can just press windows key + r on the keyboard and type appwiz.cpl and click ok.
Step 3:
Click Turn Windows Features On or Off on the upper left corner of the page.
Step 4:
Click on the .NET Framework 3.5 and click Ok to Activate.