Hello i wuld like that on my forum evry single post will have on TOP 1 ads, in wich file can i insert it?
Friend you need to rethink. If one thread has settings for 10 posts display it will display 10 ads block. Which would be against TOS. Use header, posts and footer template files to do this. But just use the adsense code once in the posts. It will give you 3 ads block on the page.
There is a phpbb mod that essentially generates a new post with your ad. I don't like the approach as well as the digitalpoint approach because the ad is not a post.