.NET Framework is a software framework developed by Microsoft that runs primarily on Microsoft Windows. It includes a large class library named Framework Class Library and provides language interoperability across several programming languages.
Programmers produce software by combining their source code with .NET Framework and other libraries.
The framework is intended to be used by most new applications created for the Windows platform.
Follow below steps for installation
Step 1: go to this link
Step 2: Select your language and click on Download button
Step 3: Double click or Run downloaded file
Note: If Framework is already installed on your Window, you will get below notification, Click Close, you do not require to install it because its already on your system. Skip all other steps.
Step 4: Select "I have read and accept the license terms." checkbox and click on Install button.
Step 5: Click Finish on Installation Is Complete screen.