MongoDB Realm Sync

Hi, I am working on a react native project and I need to implement this documentation https://docs.mongodb.com/realm/get-started/create-realm-app/ my react native app already using realm to save data offline and I need to sync that data with my backend and I still don't understand this documentation it very well and I don't know if my backend is suitable to use it or I do not know what changes I should make in my backend to implement mongodb realm sync, for reasons of time I cannot do it, take a look at the documentation and tell me what you need for us to start working, the backend and the front with react native realm are finished, it is only the configuration - realm synchronization and mongodb realm backend configuration or change somethings in my backend where i need help, my backend is simple, node js, express, mongodb, mongoose