Step 1: Open Steam.
Step 2: Hover over the 'Library' button until the drop-down menu shows.
Step 3: Click on 'Tools' from the drop-down menu.
Step 4: Scroll down until you find 'Football Manager 2014 Editor'.
Step 5: Double click 'Football Manager 2014 Editor' and follow the instructions to install it.
Keep in mind that you need version 14.1.2(the full game) or later to find the editor.