Installation process:
npm install react-native run-android or run-ios
On Android it takes the name of the file and you are done. On iOS however it is a bit more complex.
Add this to your package.json
For IOS,
Make sure you add fonts to resource Copy Bundle Resources
Make sure you have folder Resources in Xcode, somehow it was deleted and you must create, import fonts to that folder manually
Make sure using name of Family in Font book
On Android if you look in the file path “android/app/src/main/assets/fonts/”
Quick tutorial on setting up custom fonts with React Native across iOS and Android.
https://medium.com/react-native-training/react-native-custom-fonts-ccc9aacf9e5e