where will i put codes

i must put a popup code where can i put this code ?

Code:

<!-- Popup-->
<script>Pop=window.open("http://example.com" ); self.focus();</script>
<!-- Popup Sonu-->

You can place scripts in the site description for example. You find this option in "General / Configuration".

sorry i place it but popup not working

Well, it must be your code then... are you sure it works properly? I'm no script expert, so unfortunately can't help you much here. =/

One more thing. If you want to have the popup only on the main page, then you better put this code into the homepage message (General / homepage / configuration).