The additional scenery installed with Draken contains some additional navaids that simulate tactical navigation and landing systems formerly used by the Swedish Air Force. The ground stations are also modeled in the scenery. See the Flight Manual for more information.
Draken 5.0 is installed outside of the Prepar3D program folder. All versions in the 5.x series will be installed in separate folders and should not conflict. Patches/hotfixes that are issued between the release versions may overwrite files in the current installation.
Draken 4.1 is installed in its own aircraft folder and in sub-folders within the main FSX gauges and sounds folders. The effects files are specific to each version and will not conflict with previous versions. The included scenery files will be updated from earlier installations and are fully backward compatible.
Draken 5.0 is designed for Prepar3D v4 and will not work properly in earlier versions of Prepar3D or in any version of Microsoft Flight Simulator. You can install it in FSX with some tweaking, but it will look ugly and perform badly.
Draken 4.1 requires Microsoft Flight Simulator X SP2 or later. It can be installed in Prepar3D, but it will not work as intended and some major tweaking is needed. You are on your own there.
Draken 3.2 requires Microsoft Flight Simulator 2004 (FS9).
Download the installer archive and unzip the contents anywhere on your computer, then double-click on the installer to run it. You will be prompted through each step of the installation process.