Select the name of the app you're creating this ad unit for. If you don't see it in the list of recent apps, you can click Add app to add a new app or click View all apps to search a list of all of the apps you've added to AdMob.
Click Ad units in the sidebar.
Click Add ad unit.
Click Select for the Banner ad format.
Complete the settings for this ad unit:
(a) Ad Type
Choose the ad type(s) allowed to be shown in this ad unit. You can choose any combination of ad types by checking the boxes. Unchecking all of the boxes will result in an error. You must choose at least one ad type for each ad unit. Suggestion: To try and help maximize revenue for this ad unit, we suggest checking all of the boxes.
(b) Automatic Refresh
Determines how often a new ad request is generated for this ad unit. Recommended: Select Google optimized to let AdMob manage the refresh rate for you. The Google-optimized rate is calculated using AdMob historical data to ensure the ads shown in your ad units are being refreshed at the best rate for banner ads. You may also set a custom refresh rate of 30-120 seconds or disable automatic refresh rate completely.
(c) Ad Unit Name
Enter a name for this ad unit. Recommended: Include relevant information, such as ad format and location in your app to make it easier to identify later.
(d) Click Save
This documentation is still under development, we are working to add more things to it to make it complete. Keep yourself up to date by visiting this page whenever you needs any help. If heaving some issues, you can contact Support