This specific version ("Some Assembly Required") introduced key features you should explore:
: KSP_x64.exe (Recommended for 64-bit systems) or KSP.exe . macOS : KSP.app . Double-click the file to start the game. 3. Essential First Steps (In-Game) File: Kerbal.Space.Program.v1.11.1.03066.zip ...
Since the file is a .zip archive, you do not need to "install" it in the traditional sense. It is a portable version of the game. File: Kerbal.Space.Program.v1.11.1.03066.zip ...