Dropdown Section when clicking on a picture/button?

Hello

I am new to wordpress and I have literally 0 idea how to code. I played around with Plugins and widget but I could not make it work.

So what I want to do is, that when someone clicks on the “GUIDE” Button on this website: http://alcasthq.com/?page_id=106 that a windows comes up below the picture and it expands so you can see the youtube video+text without the need to open a new page.

I hope my explanation is clear, otherwise I will try to find an example.

Thank you