Adding jQuery and CSS to a SharePoint list and form

Hi all.

I've searched for answers to this question, but it seems everybody has their own way of doing it, and nobody seems to explain it clearly either!

I'm using SharePoint 2013.  I have access via the website and via SharePoint designer.

I would like to style my forms with some CSS/jQuery.

Can anybody give me a clear explanation of how I can add CSS and jQuery to a specific list/newform/editform/displayform?

Thanks.