I haven't found any advertisement button in my bb. Is it there? And if yes in which section i could find it?
Advertisement button? Who told you there was an advertisement button??
I mean the section in admin cp by which we can use ads of google adsense
Unless you installed a plugin, there is none. You could just add it into your header template.
ACP > Themes & Templates > Templates > **Your Theme** > Header Templates > header
Place the code where desired.
Which plugin should i use? Can you provide details and link to it?