Answers for "how to create user in mongodb as admi n"

mongodb add user

use <your database>
db.createUser({
  user: '<some username>',
  pwd: passwordPrompt(),
  roles: [{
    role: 'readWrite',
    db: '<your database>'
  }]
})

mongodb add admin user

use admin
db.createUser({
  user: "username",
  pwd: "password",
  roles: [ "root" ]
})