Open rn_oreo/ios/rn_oreo.xcworkspace in Xcode or run xed -b ios then you can change:
1. Change App Name
2. Change Bundle Identify
The bundle identifier is the unique string that identifies your application to the system.
Bundle identifiers are usually (not always) written out in reverse DNS notation (I.e com.myCompany.myApp).
You can bundle Identify change under app name.
3. Change App Icon
Click Assets.xcassets in the Project navigator and then choose AppIcon.
Now just drag the right sized image (in .png format) from Finder onto every blank in the app set. The app icon should be all set up now.
Referential https://stackoverflow.com/questions/28170520/ios-how-to-set-app-icon-and-launch-images
Check video guide on how to change icon by tool: https://www.facebook.com/rnlab.io/videos/2215170862111679/?v=2215170862111679