//JS file
Meteor.users.insert({
    username: 'admin',
    profile: {
                first_name: 'Clark',
                last_name: 'Kent'
    },

});

// HTML view
{{Meteor.user().username}}
{{Meteor.user().profile.first_name}}
{{Meteor.user().profile.last_name}}

<template name="user">
  <p>{{firstName}}</p>
</template>

Template.user.helpers({
  firstName: function() {
    return Meteor.user().profile.first_name;
  }
});

{{#if currentUser}}
  {{> user}}
{{/if}}

{{#with currentUser}}
    {{#with profile}}
        {{first_name}}
    {{/with}}
{{/with}}

{{#with userDetails}}
   First name:-{{this.first_name}}
   Last name:- {{this.last_name}}
{{/with}}

 //jsSide
 userDetails(){
   return Meteor.user();
 }