Not sure if I understand what you mean by “how do I launch another window automatically?”
If I take it at face value It say your looking for a simple pop-up or pop-under when your main page loads.
If this is correct the script below should work fine for you …
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Id recommend saving the actual script (between the script tags) to a .js file and loading it on the mainpage via a script call as such …
This script utilizes cookies so that the window does not automatically popup every time and annoy the hell out of your site(s) visitors …
If thats not what you were looking for let me know …