Text_field with options (youtube style)

Hello World.
I’m kinda new here and new in Ruby on Rails. I’m working now at a
personal project for learning RoR.

I searched Google and it’s true that there are pleny result about this
topic, but everything I do, I can’t make it work.

I want to have a text_field, which when I click on it, it opens a popup
(like those on google, youtube) with some “suggests” extracted from

I included the :default javascript_tag. I found something about
auto_complete_field function and tried with it. It doesn’t work.

Can everybody explain the steps I have to make, the important aspects,
what do I really need for this?

Thank you very much.