Set NDK version for react-native module

I'm trying to setup react-native skia library into project.

IOS working perfectly but not Android.

In the documentation, it's wrote :

Currently, you will need Android NDK to be installed. If you have Android Studio installed, make sure $ANDROID_NDK is available. ANDROID_NDK=/Users/username/Library/Android/sdk/ndk-bundle for instance.

I got files into this folder, so I'm supposed android NDK is installed :

ndk

But what is $ANDROID_NDK ? A variable into Android Studio ? Mine was :

variables

Then, it's wrote in the documentation :

And them the Modules section. click on shopify_react-native-skia and select NDK version with dropdown, and click on apply.

but I don't have shopify_react-native-skia module :

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Btw, in this part of settings, I have nothing on ndk field, and it is not enable to set something :

enter image description here

(I cant' post images for now because I need 10 reputations)