Ware Do I place Java Code?

I would like to add a some java script to by blog but I am not sure ware to place the Java code

Here is the code:

/* ---------------------------- */
/* SHOW-HIDE Layer				*/
/* ---------------------------- */
function showlayer(layer){
	var myLayer=document.getElementById(layer).style.display;
	if(myLayer=="none"){
		document.getElementById(layer).style.display="block";
	} else {
		document.getElementById(layer).style.display="none";
		}
}

This is the link to the Java code
https://woork.blogspot.com/2007/10/show-hide-layer-using-simple-javascript.html

Should I put this code in the header or the page Ware I am using the script

Thanks
-mike