Secure way of adding user with admin role - back end only

I am using the mean stack from meanjs.org . My question is what is the best practice for adding a user with admin role , who receives special privileges.

I can just add a admin user to at app init to mongo db at app initialisation , is that the usual pattern used. Sorry new to web dev.

Are there any config values that I can use , specific of meanjs that would allow me to set admin user credentials?

Cheers