I already programmed small chrome extension that when you click on it's icon it sends you to a specific URL.
Now I need to add an Adsense Advertisement included in my extension code, so that the ads appear at youtube.com at the right ,
Please look at the image: http://i.stack.imgur.com/yhVz5.jpg, I just marked where I want my ads to appear.
I've already seen an extension that does that, but I don't know how to do it.
AdSense in packaged apps is being worked on. See the discussion here: https://groups.google.com/a/chromium.org/forum/?hl=en&fromgroups#!topic/chromium-apps/_47r_YKRdjA
In the meantime, star this issue: https://code.google.com/p/chromium/issues/detail?id=132602
Have you read the program policies: Ads in Chrome Apps and Extensions https://developers.google.com/chrome/web-store/program_policies
Currently, AdSense may not be used to serve ads in Chrome extensions or packaged apps, per AdSense policies.