How do I install MechJeb?

There are steps to open File Explorer. You can use either PC or Finder. Click on Downloads. There is a sidebar to the left of File Explorer and the Finder. Click the zip file to open it. The files and folders need to be removed. Click the "MechJeb2" folder if you want to cut it. You can open the game. You can click the library. The Kerbal Space Program can be right-clicked.