Use jQuery to place clicked button files into target #CONTAINER.

Use jQuery to place clicked button files into target #CONTAINER.

I need the jquery codes to perform the actions for this simple webpage.
I use css file to place measurements and colors etc

SIMPLE WEBPAGE:

I need to know where to place the codes:  In the
<head>   etc  </head> or
in the web page in the <body> area.

<div id = “#header”> details in css file</div>
ex: width:200px; height:300px; etc in css file.

<div id =”#container”>Details etc in css file - Inside this (#container BOX) I want to see my other
html/php file content when button1 /2 /3 etc is clicked</div>
and not on a separate or blank page.

<div id= “#menu”>Button1 , Button2 , Button3</div>  
when any button clicked its file to show up inside the #container box.

<div id = “#footer”>If possible -  button 1 -  button 2 etc when clicked from footer
will also display the file in the #container box.

Please if you place any codes such as <span> etc let me know why? And where those
codes come into the main code.

Thanks.