Installation.

You can actually put it anywhere you want and point to that path.
In the case of installing the Single Player version, I advise you to put the file in the path (so that you have all the missions for Strike Eagle together): 

DCS World ...\Mods\aircraft\F-15E\Missions\Single

The version ending in MP is for Multiplayer only.
The SP version is singleplayer.

YoYo,
August 2023,
Regards

Btw.
video for part of this mission: https://youtu.be/9cLjtjYnEro