Download and unzip this file.
Keep everything in the Composer folder and place it somewhere convenient.
You can run the program by double-clicking on the Composer.exe file in the folder or by making a shortcut for it.
This is Version 2.6.3, which is not the absolute latest (3.1) but does have most of the capability of the latest version.
You will also want to associate .not and possibly .mid files with Notation Composer.
