third parti client interaction (android App)

Hi,
I’m a backend php developer. My website uses WSL for logging user with facebook. All works great!

Now i’m developing an android app (with react-native, doesn’t matter?).
I’m using rest api to retreiving remote data.
I have successfully added facebook sdk into my app and i got facebook access token as facebook sdk response.

I need to interact with wsl “wsl_process_login” function, because i need the wsl functionality that create new user when loggin on mobile.

How can i get wsl flow work having the facebook access token on mobile side?

thanks

Luca