trying to user sting interpolation or another rails resource method to allow controller user.id data to be viewed in a boot strap label

Question

very new and need guidance, I am a very junior dev. Working on my first project: auth. project - that i've been working on for several months. but I am hitting a wall on how to pull my user.id from my User_controller and import or pull that data into my index.html.erb view.

plan is to have "user.id". render on the page with a label field dynamically. So, if a X user signs in, that "user_id" will show on this label form field by default to show X user is signed, and create some logic later to have my controller validate user and allow to prompt a new modal to change password, but when after user is login, and it routes to /dashboard view, For what ever reason, I can't get the user_id to show in my Label >user_id< using from bootstrap. I feel like this might be easy, but I'm not sure I am fully understand how rails can inject that data resource on the page dynamically

I have tried <%= #{:user_id}%>, change the label type id:/user_id with <%= #{:user_id}%>

this is what my user.controller looks like:

class UserController < ApplicationController
   def index
    # rendering json on page: user data
      render json: User.all
   end

   def create
      user = User.new(
         first_name: params[:fname], 
          last_name: params[:lname],
          username: params[:username],
          password: params[:password],
          password_confirmation: params[:password_confirmation]
      )
      if user.save
         session[:user_id] = user.id
         flash[:success] = "text"
         #redirect_to '/login'
      else
         flash[:warning] = "text"
         #redirect_to 'register'
      end
   end

   def show
      #  render plain: params[:id]
      #render json: userdata[:users].select {|user| user.get_id() == params[:id].to_i}
      if User.exists?(params[:id])
         render json: User.find(params[:id].to_i)
      else 
         render plain: "that user doesnt exist: #{params[:id]}"
      end
   end

   def validate
      puts params
      username = params[:username]
      exists = User.exists?(username: username)
      # puts exists
      render json: {"exists": exists, "username": username}
   end
end

and this is my html.erb

<% content_for :content do %>
  <div class="container">
    <div class="row">
      <div class="col-12">
      <h1 class=display-4>Welcome to your home page </h1>
      </div>
    </div>
  </div>

  <div class="container">
    <div class="row">
      <div class="col-12">
        <div class="jumbotron">
          <p class="lead">needing to change your password - <strong class="text-success">reset your password easy</strong>.</p>
        </div>
      </div>
    </div>
  </div>

  <div class="container">
    <div class="row">
      <div class="col-12">
        <form class="row g-3">
        <div class="col-auto">
          <label for="username" class="visually-hidden">Example:user_id</label>
          <input type="text" readonly class="form-control-plaintext" id="username" value="Helloguy123@">
        </div>
        <div class="col-auto">
          <label for="password" class="visually-hidden">Password</label>
          <input type="password" class="form-control" id="password" placeholder="Password">
        </div>
        <div class="col-auto">
          <button type="submit" class="btn btn-primary mb-3">Confirm identity</button>
        </div>
      </form>


<% end %>

<%= render template: "layouts/application" %>