Expose Login API for external App

Hello, I’m trying to create an API for the mobile APP. How do I implement login from the external mobile APP?
According to the tutorials I can use wix-users-backend login() function but:
“The returned session token must be applied using the applySessionToken() function in client-side code to complete the login.”
How do I do this on the mobile app?
How do I validate subsequent API calls?

did you find a solution?