I need to leave instructions for boss while on vacation. He wants me to leave a note on how to turn on the Dell Central Processing Unit. Is there a website where I could get information that basic? If so, I would just go there and print it out.

If you visit the dell website you should be able to download a PDF file that has that information and more. Its usually called "getting started" and contains the basic information your seeking.

Just an FYI, when you press the power button on the case/tower, it also turns on other parts of the computer and not just the processor. ;)

There is a universal symbol for a power button.