Clean Portfolio Theme – Quick Guidance Needed

Hi There, I am using "Clean Portfolio Theme" and I need guidance in few things. I would really appreciate your help. 1: I see "Portfolio" display option in "Theme Options - Customize". How can I display the work? I mean, where am I supposed to make the pages/post so I can select the Portfolios in this option? 2: What size is the Header banner supposed to be on the Homepage? 3: Whenever I click on any section of the website to "Inspect" - it shows only one class "Overlay" and because of this am unable to find the class to change the CSS. Kindly advise on this please. For reference: http://www.rhweb.ca/ Thanks & Regards, Rashida H.