I\'m confused about AdMob. I just signed up and I want to put ads in an app. I went to add site/app thinking this was it. There is a question and field that says Android pac
Though its an older post, but still if it helps anyone who wants to display ads in their app. Based on many of findings with friends I would suggest to look for other ad network than admob. Imagine you set all things right, follow rules correctly, feel happy about your earnings through ads on your admob console and then suddenly one fine day you get an email from google admob that your account is suspended for invalid activity. Well what does it mean? In simple terms, it means google don't tell you what did you do wrong and will keep all your earnings. It's natural for every newbie developer to settle with admob being google's own ad network. But dont fall for this trap, if you don't want to lose your money better avoid admob.
It would be nice if readers share their experience with other ad network. It can help all of us I think.
When signing up for AdMob they want to see where your application currently is, but this isn't an essential part of the process from your point of view.
Basically, for AdMob (as well as a whole slew of other similar sites) you download a small SDK that you include in your Android application. This SDK usually has a View that you can plop on one of your Activities. You give that control some information, like a private AdMob key (so it knows which person you are) and then that control will provide an ad from the server. Note: it usually doesn't work right off the bat and there is a "development mode" setting you can set to always pull back a fake ad while you are just working on it.
You may also want to sign up for multiple sites and check out AdWhirl which allows you to manage the ratio of ads you display from each site, since you will find that some sites will generate more revenue for you than others.
Good luck!
Edit: I put this in a comment originally, but seemed suited better as an answer.
Google keeps switching the location of the Admob integration instructions which is driving me nuts. It has moved 3 times in the past 6 months. It originally was nicely done in wiki format, then moved to a PDF and now it is part of the Google code website which is here.
On this site you will find what you need, but unfortunately, you will have to dig a bit to get everything you need.