I got an engine block heater from Ford the other day and was told to "pop out one of the freeze plugs and put it in there."

Where can I find these on my 1999 4.6L Triton? There are some very sketchy drawings in the Ford manual, but I can't tell where the plugs are from them.

Do I have to remove anything else to get to them? How exactly do I "pop" them out?

Thanks for any assistance.