Note: This was tested on Windows 10.

1. Download the zip file which contains the spatialite binaries.
2. Extract the contents of the downloaded zip file to a directory called C:\Program Files (x86)\Spatialite. (You will probably have to make this directory.) After completing this step, there should be a file at C:\Program Files (x86)\Spatialite\spatialite.exe.
3. Once the installer is finished, add the directory C:\Program Files (x86)\Spatialite to your system path. A tutorial for adding directories to your system path can be found here.

4. Test your installation by opening a new Command Prompt window, typing spatialite -version and pressing enter. If you see something like the following, installation was successful:

   C:\Users\mq20151400>spatialite -version 3.8.11.1 2015-07-29 20:00:57 cf538e2783e468bbc25e7cb2a9ee64d3e0e80b2f