Why can't my portfolio page take a portfolio?

I’m a bit stuck here. I bought the Freelo theme thinking I would only need to swap the current assets with mine and my website would look like the demo advertised with the theme sale ad.
I have created the pages, built the navigation, now I’m trying to make each page look like the demo and I’m going nowhere.
What is the process? I have looked at the documentation. There is nothing there explaining how to ad the beautiful portfolio seem in the demo to the customer’s website…
To ad the demo’s portfolio:
I go to Pages > choose one and click “edit” > click on switch to “Page Builder” > click on the “+” sign on the Visual Composer > ad the “portfolio” item > Then go to Portfolio > add a new item > switch to “Page Builder” > choose “add element” > choose “image” > select the image > click “save changes” > then “publish”. Nothing happens…
What is the secret? Where am I missing so terribly?

Thank you.