AdMob is a famous platform of Ad-Network which allows you to monetize your app/games with Google Ads and earn revenue. Check following links for complete guideline about how can you integrate AdMob into your app:
There is no any trick to monetize your app with your StartApp account. Just do follow simple steps and integrate your StartApp into your apps of below mentioned tutorial:
It seems tricky to integrate your app with your UNITY ads but after having this tutorial and doing all steps in sequence, you can easily monetize your app with UNITY ads. Please visit following link for detailed tutorial about Unity ads integration: