Watson Assistant "context variable"

I am using Node-RED for making a UI, this UI has a registration form with input fields as:

  1. Name:
  2. Email:
  3. Age:
  4. Phone no.

my goal here is to have my Watson Assistant know the name of the user before the user starts to chat with the bot.

So, technically there has to be a node that feeds the assistant node with the user_name and user_email so as to have the bot greet the user as:

Hey "$name" how may I help you?