The first step to making money in your app with AdMob is setting it up. Published and unpublished apps can be added. If you set up an unpublished app, you'll need to come back to AdMob and link the app to its app store entry later when it's published.

Complete the following steps to set up an app.

Set up a published app

1. Sign in to your AdMob account at https://apps.admob.com.
2. Click Apps in the sidebar.
3. Click Add app. A dialog box appears.
4. Click Yes.
5. Enter the name of the app and click Search.
6. Click Add beside the app you want to add. 

Set up an unpublished app

1. Sign in to your AdMob account at https://apps.admob.com.
2. Click Apps in the sidebar.
3. Click Add app. A dialog box appears.
4. Click No.
5. Enter the app name.
6. Select a platform.
7. Click Add.
8. Click Add ad unit to create an ad unit for this app or click I'll do it later to exit the page.

When it's published, you can return to AdMob and link your app to its app store entry.

Detail: https://support.google.com/admob/answer/2773509?hl=en