Google has a 'heat' map which discusses the best places to put their add in forums. You can find it in your Google Admin area.
To locate those specific templates go to vbulletin.com. They have a good tutorial on this. I was able to follow it, and I'm pretty 'slow' when I comes to messing around with templates.
Does anyone know where to paste the code for google ad sense?
Thanks
That all depends on where you want the ads to show up. I like them under the first post in every thread. You can also use conditionals so you can control who sees them and who doesn't.. This comes in handy if you have people willing to pay for add free browsing.