How to make NextAuth consume API from my custom backend e.g. Nestjs

[Axselll]

Hi, sorry to bother you guys, i just want to ask about nextauth consume api from backend.
so i created a backend let us just say i use nestjs, i created a google login endpoint when i call the endpoint it will redirect me to google login prompt/consent page and it will return an access token. my question is How do i fire that endpoint from NextAuth ?? THANKS IN ADVANCE