How do I use tidy ?

I have read the section on how to run tidy on this webpage,

http://www.w3.org/People/Raggett/tidy

but I don't see how to follow the instuctions; Specifically:

How to run tidy

            tidy [[options] filename]*

How do I use this ? How do I put any input into the program ?
Then later it says : To get a list of available options use:

            tidy -help

How do I use this  line ? I type it in, press enter,  and nothing
happens.


Red