How to build on Android / iOS

1- Open Build Settings…2- Select Android or iOS and Switch platform

2- Select Android or iOS and Switch platform

3- Then Build and Run

Next only for iOS:

4- After building open the result project in xCode.

5- If you using Admob - download Google Mobile Ads SDK https://developers.google.com/admob/ios/download

6- Copy GoogleMobileAdsSDK.framework to your xCode project/Frameworks

7- Drag GoogleMobileAdsSDK.framework from your xCode project to Build Phases->Link Binary With Library

8- Then select your device and press Build.

Read more in official guides:

iOS and Android