Click on the icon for the WHDLoad install, hold down right mouse button, select 'Icons -> Information...' from the menu at the top, Click on 'New' in the window that opened and enter:
Press return and click on 'Save'.
You should already have a 'WHDLoad.prefs' in the WHDLoad archive. Just copy it to 'S'. Remove the ';' in front of a line to activate it (; = comment).