Ok, your new post makes it a bit easier to help you. The error saying "Unable to open your tool Installer" means that you are missing the tool called Installer. It should be placed in the C: drawer. I think you can download it from Aminet, but IIRC the file is also somewhere on your Install 3.1 disk.
Before you get the install script for WHDLoad running you will not be able to run any WHDLoad software. The error code you are describing could be two things. Either you haven't got a fully installed WHDLoad game, or the WHDLoad file is missing. This file should also be placed in C:
There is no need to copy the WHDLoad archive drawer to C:, as the files you need will be copied by the installer. Therefore it's not enough to place the whole drawer in C:, as Workbench still won't be able to find the WHDLoad tool.
However, you can copy the WHDLoad tool by hand. Go to the WHDLoad drawer (from your description it sounds like this would be WB:C/WHDLoad) and enter these lines :
Copy C/WHDLoad to c:
Copy C/DIC to c:
Copy C/Patcher to c:
Copy C/RawDIC to c:
Copy S/WHDLoad.prefs to s:
Now you have WHDLoad installed, so enjoy :-)