You no longer need to enable each app for iAd in the Manage Your Apps module in iTunes Connect.
After you sign the iAd App Network Contract and integrate the iAd Framework into your app, you approved and "Ready for Sale" apps will all be eligible to receive iAd ads.
At iTunes Connect you can see your reports at the iAd module.
Its very easy now. Just show Ads via Ejecta for example. (Tip for Ejecta: You have to add some lines to display the advertisements banners correctly.)
With iAp I have no experience yet.