first baby steps in Dreamweaver CC 2017

Hi,

"Absolute novice and reluctant coder: here.

Well I've given in and decided to use Dreamweaver after all. I've spent all day trying to get to grips with it without a great deal of success.

I'm trying to edit my site which is Seignaletplus.com I've got the home page on Dreamweaver and managed to import the CSS file from my site and it works fine with the home page. Among other edits, I'm trying to make the site more mobile friendly. It loads pretty much ok on a mobile I think. The two side panels disappear which is fine. Links to that content appear in the main body as well, so that's ok. Now I'm trying to remove all the top page links and put them on a dedicated "menu page" and just have that menu symbol thingy instead on all the pages. A Hyorglypticon or whatever it's called.

So I've started a new page called /menupage. I've copied and pasted just the HTML code for the top panels and the two side panels into /menupage.
But the CSS is not working on that page. So questions:

1.How do I get Dreaweaver to show me the CSS input from the style sheet and why is it working for the index page and not my new menupage?
2.I shouldn't really ask this. I should work it out for myself but I've been struggling all day. What commands do I need to use in Dreamweaver to make the top page links which are now going into the menupage responsive? Please don't do it for me and give me the source code. I need to work it out for myself.

Cheers Chris