1) Make sure you have an installed copy of WolfEdit 1.1 lying around on your hard drive. NOTE: IF YOU ARE GOING TO BE INSTALLING BREAKTHROUGH INTO A FIRST ENCOUNTER COPY OF WOLF3D, YOU SHOULD NOT USE WOLFEDIT 1.1A. IF YOU DO, BAD THINGS MIGHT HAPPEN.
2) Double-click the Breakthrough icon. WolfEdit should open and a level window should appear.