You have to understand that there are functions for the server, and there are for the client, and there are common ones that work on the client and on the server.
You need to start with the simplest.
And since you need an entry in meta.xml, study this.
-- client functions
-- client events
-- server functions
-- server events
P.S But start writing the simplest scripts, first on the client / server, and then learn how to work simultaneously with the client and server.